Green chemistry in analytical atomic spectrometry: a revie · Green chemistry in analytical atomic...

Dynamic Article LinksC<JAAS

Cite this: J. Anal. At. Spectrom., 2012, 27, 1831

www.rsc.org/jaas TUTORIAL REVIEW

Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54

. View Article Online / Journal Homepage / Table of Contents for this issue

Green chemistry in analytical atomic spectrometry: a review

C. Bendicho,*a I. Lavilla,a F. Pena-Pereiraab and V. Romeroa

Received 20th July 2012, Accepted 3rd September 2012

DOI: 10.1039/c2ja30214d

As a result of the greater consciousness within the analytical community on the impact of chemicals on

human health and environment, green issues are increasingly taken into account when choosing an

established analytical method or developing a new one. Apart from typical analytical characteristics

(e.g., sensitivity, limit of detection, repeatability, etc.), other features such as the amount of sample/

reagents, operation time, use of energy-effective apparatus, waste production, etc. should be

highlighted in order to meet the principles of Green Chemistry. Although conventional approaches for

trace element analysis by atomic spectrometry usually involve well-established sample pre-treatments

based on ‘wet chemistry’, and high consumption of gases, reagents, etc. is inherent to many techniques

in this group, there are still many avenues where green issues can be implemented. For greening atomic

spectrometry, green chemistry principles should be applied to every step of the analytical process, i.e.,

from sampling and sample pre-treatment to data processing. In this review, main pathways for greening

atomic spectrometry such as downsizing of instrumentation, use of portable instruments, solid

sampling, application of clean energies (ultrasound, microwaves, etc.) for sample pre-treatment,

development of on-site, on-line and at-line approaches vs. typical off-line methods, application of

modern extraction techniques (e.g., solid- and liquid-phase microextraction), green solvents and

derivatization agents and use of chemometric tools for method optimization, signal processing, etc. are

discussed in a critical way.

1. Introduction

In recent years, an increased interest has arisen in the analytical

community for the implementation of the principles of Green

Chemistry. Several of the twelve principles established by

Anastas and Warner1 more than 10 years ago are directly con-

nected with Analytical Chemistry, such as prevention of wastes,

safer solvents and reagents, energy efficiency, renewability,

reducing derivatives, real-time analysis and accident prevention

through implementation of safer chemistry. In the last two years,

the subject has deserved attention in several books2,3 and

reviews,4–15 and the concept ‘Green Analytical Chemistry (GAC)’

has been increasingly employed.

Several trends have driven for long the research on new

detection methods such as miniaturization, automation,

simplification and acceleration, which in turn are related to

many of those principles. Implementation of those trends in the

analytical methods has usually provided not only enhanced

analytical characteristics, but also significantly improved

greenness profile.

aDepartamento de Qu�ımica Anal�ıtica y Alimentaria, �Area de Qu�ımicaAnal�ıtica, Facultad de Qu�ımica, Universidad de Vigo, Campus AsLagoas-Marcosende s/n, 36310 Vigo, Spain. E-mail: [email protected];Fax: +34-986-812556; Tel: +34-986-812281bCESAM & Department of Chemistry, University of Aveiro, 3810-193Aveiro, Portugal

This journal is ª The Royal Society of Chemistry 2012

Although some workers have addressed the greening of

analytical techniques such as chromatography8,14 or molecular

spectroscopy12 and mainly oriented toward the determination of

organic analytes,13 to the best of our knowledge, no review or

monograph has been specifically focused on the implementation

of GAC principles in analytical atomic spectrometry.

At present, there is a growing interest in developing green

methods using atomic spectrometric techniques. Fig. 1 shows the

evolution of the publications devoted to green analytical chem-

istry in atomic spectrometry since 2000 following the subjects:

‘green’, ‘greener’, ‘clean’, ‘cleaner’ and ‘environmentally friendly’

atomic spectrometry. Fig. 2 shows the corresponding literature

sources.

The implementation of GAC principles in the analytical

atomic spectrometry field demands for a close knowledge of the

ways for greening every step of the analytical procedure,

including sampling, preservation, sample pre-treatment,

measurement and data processing. In order to establish a metric

of the greenness related to any analytical protocol, issues such as

the type of solvent, apparatus and method should be focused.

Some attempts have already been made to assign a greening

profile, e.g., National Environment Methods Index (NEMI)

database,16 according to the properties of reagents and wastes

generated. Recently, Namie�snik’s group has proposed a novel

metric approach so that new or modified analytical methods can

be compared in respect to greenness.17 Ideally, a green method in

J. Anal. At. Spectrom., 2012, 27, 1831–1857 | 1831

http://dx.doi.org/10.1039/c2ja30214d





http://dx.doi.org/10.1039/C2JA30214D

http://pubs.rsc.org/en/journals/journal/JA

http://pubs.rsc.org/en/journals/journal/JA?issueid=JA027011

Fig. 1 Evolution of the publications devoted to green analytical chem-

istry in atomic spectrometry since 2000using the subjects ‘green’, ‘greener’,

‘clean’, ‘cleaner’ and ‘environmentally friendly’ atomic spectrometry

(source: ISI Web of knowledge (Web of Science) – Thomson Reuters).

Fig. 2 Evaluation of the publications devoted to green analytical

chemistry in atomic spectrometry as a function of the corresponding

literature sources since 2000 using the subjects ‘green’, ‘greener’, ‘clean’,

‘cleaner’ and ‘environmentally friendly’ atomic spectrometry (source: ISI

Web of knowledge (Web of Science) – Thomson Reuters).

Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54

. View Article Online

atomic spectrometry should involve small reagent/sample

consumption, energy-efficient apparatus, safe operations, short

total times for analysis and avoid the use of toxic/hazardous

reagents.

An assessment of different strategies carried out in every stage

of the analytical process according to their ‘greenness profile’ for

trace element analysis and speciation by atomic spectrometry is

provided in Table 1.

1832 | J. Anal. At. Spectrom., 2012, 27, 1831–1857

Undoubtedly, the maximum greening profile is achieved with

methods carried out on-site using portable instrumentation.2,3 In

this case, neither preservation nor pre-treatment procedures are

required and transport to the lab is also circumvented. Unfor-

tunately, unlike other analytical techniques (e.g., photometry,

electroanalysis), the instrumentation available for atomic spec-

trometry is difficult to adapt for field analysis without any sample

pre-treatment, although some efforts have been made in this

direction (e.g., portable X-ray fluorescence spectrometers,

portable laser-induced breakdown spectrometers, miniaturized

atomizers for atomic absorption spectrometry, etc.). In the

present state of the art, portable instruments based on atomic

spectrometry principles are, in general, far from fulfilling the

outstanding analytical performance of conventional instruments

available in labs.

The solid state is perhaps the one that requires the most

stringent sample pre-treatment for determination of trace

elements by the wide-spread atomic spectrometric techniques.

Therefore, one of the most realistic options to meet GAC

requirements is direct analysis with little or no sample pre-

treatment. In this way, solid analysis including direct solid

introduction and slurry sampling into the atomization system

has been known for long as an efficient way to overcome wet

chemistry that includes non-green operations, i.e., use of corro-

sive mineral acids, potential risks inherent to the application of

high pressures and heating, high energy consumption, etc. When

no direct analysis is feasible, an enhanced greening profile can be

reached using activation of sample pre-treatment by efficient

energies such as microwaves, ultrasound, UV radiation, etc.11,15

These processes generally involve less concentrated reagents and

safer operation conditions.

As an intermediate situation, on-line and at-line analyses

represent a jump toward GAC concepts in atomic spectrom-

etry, involving automated or semi-automated operation and

generally lower consumption of reagents. On the opposite side,

off-line methods, which are typically recommended in many

official methods of analysis, do not fulfil most GAC

requirements.

Examples where pre-treatment is maintained but a drastic

decrease in the amount of reagents occurs are the group of

modern miniaturized separation techniques. Preconcentration,

matrix removal, derivatization and other typical processes

required for trace element analysis and speciation can be easily

simplified and integrated by resorting to solid and liquid-phase

microextraction approaches (e.g., Ref. 9).

Fig. 3 shows a variety of green strategies resulting from the

passage of atomic spectrometry through the optics of green

chemistry. According to this, pathways toward the achievement

of greener atomic spectrometry methods would include the

following.

(a) Development of on-site, on-line and at-line methods in

contrast to traditional off-line methods.

(b) Decreasing the use of reagents, sample consumption (use of

microsamples) and derivatizing agents, or even better, to apply

direct analysis without reagents.

(c) Replacing traditional separation methods (e.g., liquid–

liquid extraction, LLE) by other methods involving miniaturized

approaches (e.g., solid- and liquid-phase microextraction), with

the subsequent reduction of solvents.



Table

1Greennessprofile

ofdifferentstrategiescarriedoutfortrace

elem

entanalysisandspeciationateach

stageoftheanalyticalprocess

Greennessprofile

Preservation

Sample

dissolution

Derivatization

Separation

Measurement

Data

processing

Low

Additionofchem

icals

forpreservation

Wet

digestionwith

mineralacids

Harm

ful,unstable,toxic

derivatizationagents

Solventextractionusing

largevolumes

oftoxic

organic

solvents

(e.g.,

benzene,

CHCl 3,etc.)

Conventionalapplication

ofatomic

spectrometric

techniques

such

asFAAS,

ICP-O

ES,etc.

Univariate

approach

formethodoptimization

Open

vessel

digestion

Organic

solvents

and

multistageprocedures

forderivatization(e.g.,

Grignard

methodfor

organometals,West€ o€ o

methodforHg,etc.)

Conductiveheating

(e.g.hotplate)

Interm

ediate

—Energy-efficient

treatm

ents

(MW,

US,UV

radiation,

etc.)

Derivatizationin

aqueous

phase

(e.g.,ethylationfor

speciationoforganometals

byhyphenatedtechniques)

Miniaturizedextraction

techniques

(e.g.,SPE,

LPME,SBSE,SPME)

Applicationofsensitivetechniques

insteadofusingpreconcentration

withclassicalmethods(e.g.use

ETAASinsteadofFAAS

combined

withsolventextraction)

—

Smallvolume

digestion

Use

ofenergy-efficient

methods(focusedMWs,

ultrasound,etc.)for

extractionofspecies

Mem

braneseparations

Softextractions

(e.g.UAEinsteadof

complete

dissolution)

Surfactants

(e.g.,

cloudpointextraction)

Advancedoxidation

(e.g.,UV/H

2O

2,UV–US,

photocatalysis,etc.

insteadofchem

ical

oxidants)

New

sorbents

based

onnanomaterials

Efficientsample

introduction

system

sinsteadof

conventionalnebulizers

Modernsolid–liquid

extractiontechniques

(SFE,ASE,etc.)

Automatedon-line

system

sallowingsample

pre-treatm

ent,

separations,etc.

(FIA

,SIA

,multicommutation)

Non-chromatographic

approaches

forspeciation

analysisofsampleswith

afew

species

High

Onsite

analysis

withoutpreservation

Solidsampling:direct

solidsamplingandslurry

sampling(SS-ETAAS,

ETV-ICP-O

ES,ETV-

ICP-M

S,GD-ICP-O

ES,

TXRF,LIB

S,etc.)

Photochem

ical

vapourgeneration

Solventlessseparation

techniques

(e.g.,SPME

withthermaldesorption)

Miniatomizerswith

low

consumption

ofgases

Multivariate

approaches

formethodoptimization

(e.g.,factorialdesign)

Electrochem

ical

vapourgeneration

Miniaturizedseparations

(e.g.,microchips)

‘In-atomizer’trapping

techniques

insteadof

preconcentrationby

chem

icalprocedures

Chem

ometrictoolsfor

treatm

entoflargeamount

ofdata

inorder

toextract

hidden

inform

ation

Ultrasound-promoted

cold

vapourgeneration

Green

solvents

(e.g.,ionic

liquids)

Miniaturizedflow

system

s(lab-on-valve,lab-on-a-chip)

coupledto

atomic

detectors

Green

interfacesbetween

HPLC

andIC

P-M

S,AFS,

etc.

forspeciationbasedon

nanomaterials(e.g.

UV/nano-TiO

2)

Solventlessmethods

forspeciation(purge-and-

trap,cryotrapping,etc.)

Screeninganalysisusing

portable

instruments

(on-site)

Multivariate

calibration

approaches

Nanoflow

HPLC

for

hyphenatedtechniques

inspeciationanalysis

This journal is ª The Royal Society of Chemistry 2012 J. Anal. At. Spectrom., 2012, 27, 1831–1857 | 1833

Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54



Fig. 3 Relevant areas of improvement for increasing the greenness of

atomic spectrometry after filtering through the standpoint of green

chemistry.

Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


(d) Use of green solvents and derivatization reagents (e.g.,

ionic liquids, ILs) in the analytical methodology.

(e) Removal or simplification of the sample pre-treatment

stages, using energy-efficient procedures (e.g., application of

ultrasound, microwaves, UV light in pre-treatment operations).

(f) Extraction of the maximum information from analytical

data using chemometric tools that facilitate calibration, method

optimization, signal acquisition, etc.

(g) Development of automated analytical methods using flow-

injection, sequential injection or multicommutation approaches.

(h) Development of automated and miniaturized methods

based on lab-on-valve (LOV) approaches and micro-total

analytical systems (m-TASs).

(i) Design of new instrumentation for greening atomic

spectrometry.

The aim of this review is to show these possibilities so that

users of atomic spectroscopy techniques can acquire criteria in

order to implement green chemistry concepts in labs devoted to

trace element analysis and speciation.

2. Green sample preparation in atomic spectrometry

Sample preparation is undoubtedly considered as an essential

stage in the analytical process. The isolation and preconcentra-

tion of target analytes, as well as the performance of a clean-up

step when dealing with complex matrices, are the main objectives

pursued at this step of the analytical process. In the last few

years, many efforts have been taken towards the development of

environmentally friendly sample preparation approaches in

analytical chemistry. In this section we provide an overview of

those sample treatment approaches and related green issues that

are directly relevant to the development of sustainable analytical

procedures for total element analysis and speciation.

2.1. Green extraction techniques: different variants of solid and

liquid phase extraction

Sample preparation techniques such as solid-phase extraction

(SPE), solid-phase microextraction (SPME) and liquid-phase

microextraction (LPME) have represented a step forward in the

development of versatile treatment techniques and, in general,


they also fulfil the requirements so as to be considered as green

sample preparation techniques.

The development of the above mentioned sample preparation

approaches has allowed the downscaling of the sample and

organic solvent volumes needed to perform a single analysis, thus

giving rise to a significant reduction in the amounts of residues

typically generated.

The SPE technique allows the preconcentration of analytes in

short extraction times for total element and speciation anal-

ysis.18 It should be highlighted that in spite of high reduction in

solvent consumption when compared with LLE, the amounts of

solvent needed to perform a single SPE are generally in the

range of 5–15 mL.19 In the last few years, the performance of

SPE systems has been improved with the introduction of novel

materials that show higher adsorption capability, selectivity

and/or lower cost of preparation, including ion-imprinted

polymers, biosorbents and nano-sized particles.20 The applica-

tion of on-line SPE procedures with green sorbents has also

been reported. Chen et al.21 proposed the employment of a

hydrophilic ionic liquid (1-chlorovinyl-3-methylimidazolium

chloride, NmimCl) immobilized onto a polyvinyl chloride

(PVC) substrate as a green SPE sorbent to carry out speciation

analysis. In this work, Cr(VI) was determined by retention via

anion exchange and electrostatic interaction with a mini-column

containing PVC–NmimCl particles. Cr(III) was pre-eliminated

by using a strong acidic styrene type cation exchange resin mini-

column, thus allowing the speciation analysis of Cr by electro-

thermal atomic absorption spectrometry (ETAAS) and induc-

tively coupled plasma-mass spectrometry (ICP-MS). The on-line

SPE system improved the sample throughput and provided an

enhancement factor of 23.4 when using 2 mL sample volumes.

Tian et al.22 employed mungbean-coat as a biodegradable

adsorbent for on line-SPE. Cadmium was retained and enriched

in the mini-column, presumably via coordinative interactions

with the carboxylic acid groups of the bean-coat. The retained

cadmium is then eluted with 70 mL of 1 mol L�1 HNO3 and

determined by ETAAS.

The inception of miniaturized sample preparation techniques

such as SPME23–25 and LPME9,26,27 has represented a break-

through in GAC. In fact, both SPME and LPME are (virtually)

solventless techniques that allow the achievement of large

enrichment factors mainly as a result of their highly reduced

extractant-to-sample volume ratio. Hence, the SPME process

can be completely carried out without the employment of organic

solvents when thermal desorption is performed after the micro-

extraction process, while LPME techniques generally use an

almost negligible volume of extractant phase (1–100 mL). Several

microextraction modes are nowadays feasible for the extraction

of a given analyte as a function of its physicochemical properties.

However, the different microextraction modes can differ signif-

icantly in terms of greenness depending on the volume and

properties of the extractant phase, additional reagents needed to

perform the extraction process, the number of steps involved

and, in the case of SPME, the desorption conditions. A deriva-

tization step is generally required to efficiently extract and pre-

concentrate target analytes by SPME or LPME when dealing

with total element and speciation analysis. Thus, both neutral

complex formation and in situ chemical vapour generation

(CVG) are mainly employed with this aim.28



Fig. 4 Schematic representation of relevant miniaturized sample prep-

aration techniques.

Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


Another sample preparation technique that has been

employed with the aim of total element determination and

speciation analysis is stir bar sorptive extraction (SBSE).29–31

Like SPME, this technique is based on the extraction of analytes

onto a polymer-based coating. As a larger mass of polymer is

involved as compared to SPME, enhanced extraction efficiency is

achieved. Like SPME, SBSE is characterized as a fully solvent-

less sample preparation technique when thermal desorption is

selected. A special thermal desorption unit is generally used when

SBSE is combined with gas chromatography (GC) due to the

non-fitting geometry of the coated stir bar and the injection port,

respectively.32

Fig. 4 shows a schematic representation of the main minia-

turized extraction techniques discussed above.

Even though the miniaturization of a conventional method

generally involves positive aspects in terms of solvent

consumption and waste reduction, we should stress that the

employment of a miniaturized sample preparation technique is

not enough to classify an analytical method as green. In fact,

several examples can be found in the literature where reagents

and/or organic solvents displaying certain toxicity are used with

microextraction approaches, as can be shown in Section 2.4.

2.2. Green methods for treatment of solid samples

Conventional sample preparation methods for decomposition of

solid samples for analysis by atomic spectrometric techniques

involve the addition of high amounts of additional reagents and


oxidizing acids, as well as high temperatures for matrix decom-

position. These conventional pre-treatment methods are not free

from drawbacks, including risk of contamination, analyte losses,

extended decomposition times and large energy consumption.

The use of microwave (MW) and ultrasound (US) energies, as

well as the use of organic solvents, carbon dioxide and water at

both subcritical and supercritical conditions has led to the

development of a plethora of sample preparation approaches for

solid samples that meet the greenness criteria to a lesser or

greater extent.

MW energy is commonly used for both digestion and extrac-

tion procedures. Unlike conductive heating systems typically

used, MW-assisted digestion (MAD) involves homogeneous

heating of the sample by dipole rotation and ionic conduction,

thus improving the matrix decomposition process in terms of

time and energy consumption, lower volume of acids needed, and

lower blanks obtained.19

The application of small volume polytetrafluoroethylene

(PTFE) closed vials for greener MAD of breast biopsies has been

recently proposed by Millos et al.33 The use of three vials of low

capacity (6 mL) inserted into a commonly used MW digestion

vessel allowed the simultaneous matrix decomposition of small

biological sample sizes (20–30 mg) prior to multielemental

determination by ICP-MS using reduced volumes (0.3 mL per

sample) of HNO3.

MW-assisted extraction (MAE) exploits the increased solvent

diffusion of an extractant heated by MW energy to extract and

solubilize target analytes present in a sample matrix. Both pres-

surized (PMAE) and focused (FMAE) MAE can be performed,

FMAE being recognized as highly efficient for the extraction of

organometallic compounds.19 As a proof of concept, FMAE has

been exploited for the solid–liquid extraction of organometallic

species of Hg and Sn in solid environmental samples.34 The use of

disposable MW glass vessels avoided possible contamination

risks and allowed the extraction of a batch of 10 samples in less

than 1 h using acetic acid : methanol (3 : 1) or diluted tetra-

methylammonium hydroxide as the extractant.

As pointed out above, US energy is also employed for diges-

tion and extraction purposes. Acoustic cavitation produced by

US irradiation provides unique conditions that are exploited for

improving the greenness profile of analytical methodologies,

including reduced operation times, lower energy requirements,

reduced amounts of solvents and lower risk of contamination

and/or analyte losses.15 A variety of US-based systems, namely,

US bath, US probe and cup horns/sonoreactors, are nowadays

commercially available.15,35 When applied to solid matrix

decomposition, US energy avoids the use of drastic temperature

and pressure conditions, even though the use of concentrated

acids is still mandatory. On-line MAD can be used to speed up

matrix decomposition of liquid extracts and slurries, hence

avoiding the high cooling times required before the digestion

vessels can be opened. For instance, G�omez-Ariza et al.36 per-

formed chiral speciation of selenomethionine in pre-treated

breast and formula milk samples by coupling high performance

liquid chromatography (HPLC)–hydride generation (HG)–

atomic fluorescence spectrometry (AFS) with on-line MAD.

The use of US energy in combination with enzymes (hydro-

lases) has been recently proposed for the rapid decomposition of

solid samples under mild conditions. US-assisted enzymatic



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


hydrolysis has been applied for total trace element analysis and

speciation, even though further work is needed to carefully

control the effect of US irradiation on the stability and activity of

hydrolases. As an example, Moreda-Pi~neiro et al.37 have applied

ultrasound assisted-enzymatic hydrolysis of seafood samples for

As speciation. The use of pepsin as a proteolytic enzyme together

with ultrasound irradiation allowed achieving the enzymatic

process in short times.

US irradiation can also contribute to accelerate the solid–liquid

extraction of elements from solid matrices. When compared with

the related sample preparation techniques mentioned above, the

extraction time is commonly reduced with US-assisted extraction

(UAE), and moreover treatments are performed at atmospheric

pressure and room temperature. Diluted acids and soft extrac-

tants under mild conditions are employed in UAE for total trace

element analysis and speciation, respectively. Costas et al.38

employed UAE as a sample pre-treatment for extraction of rare

earth elements in seafood tissues prior to ICP-MS analysis. UAE

involved the use of diluted acids and reduced extraction times,

yieldingmuch lower volumes of acidic waste thanMAD.A clean-

up of the extracts with a C18 cartridge was mandatory to remove

organic matter prior to ICP-MS analysis.

The use of fluids in the supercritical state has also been

considered as an efficient sample preparation technique for the

extraction of target compounds from complex matrices. The

unique properties of supercritical fluids, namely, much lower

viscosity and diffusion coefficients than in the liquid state, cause

an enhancement of mass transfer and solubilisation processes.

Thus, supercritical fluid extraction (SFE) has been used in several

areas, CO2 being by far the most employed supercritical fluid due

to its non-toxicity, non-flammability, economy and availability.

Even though SFE involves short extraction times and minimal

organic solvent consumption, as well as suitability for automa-

tion, it has been superseded by alternative sample preparation

techniques, mainly due to the poor robustness of early

commercial SFE systems, the lack of standard extraction

procedures and the requirement of clean-up procedures after

SFE of certain samples.39 As for the extraction of metal species

and organometallic compounds by SFE, the use of an organic

modifier of supercritical CO2 is generally mandatory due to its

limited capability of leaching polar or ionic analytes. In addition,

ion-pair formation and complexation are usually performed in

SFE to extract charged species.40

The use of fluids at high temperature and pressure in such a

way that they are kept at subcritical conditions has also been

reported for extraction of analytes from solid samples. Pressur-

ized liquid extraction (PLE) makes use of both organic solvents

and water as extractants. The physicochemical properties of

water are highly modified when the temperature is increased

between its boiling point and critical temperature, the relative

permeability being decreased on increasing the temperature.

Extraction of metals by pressurized hot water extraction is

commonly performed by using diluted acids as modifiers.41 In

general, PLE involves the use of relatively low volumes of

extractants (10–40 mL), causing the extraction process to occur

in reduced times. However, the obtained extracts using PLE

usually require a clean-up to remove co-extracted compounds,

which extends the sample pre-treatment time before the

analysis.42


2.3. Membrane and surfactant-based sample preparation

Membranes act as selective barriers that allow the contact of the

sample solution with an acceptor phase. They allow the enrich-

ment of target analytes and sample clean-up using lower volumes

of organic solvents than conventional sample preparation

methods, such as LLE or SPE, being also suitable for minia-

turization. Thus, membrane-based extraction techniques are

being considered as environmentally friendly sample preparation

approaches.6,43 Accordingly, membranes can contribute to

greening analytical procedures. However, the green profile of

membrane-based methods will depend to a large extent on the

reagents and solvents used.

Membranes have been used in a variety of configurations for

sample pre-treatment, including hollow fibers, flat-sheet

membranes and membrane bags, and employed for trace element

analysis and speciation.44,45

A flat sheet supported liquid membrane (SLM) was reported

for Hg separation using polyvinylidenefluoride as the supporting

material, trioctylamine as the carrier, coconut oil as the diluent,

and a diluted NaOH aqueous solution as the stripping phase.46

Peng et al.47 employed a hollow fiber (HF) SLM extraction

system in combination with ETAAS for determining Cd in

diluted seawater samples. A liquid membrane was prepared by

filling the pores of a polypropylene HF with a 1-octanol solution

containing a mixture of dithizone (used as a carrier) and oleic

acid, using a 0.05 mol L�1 HNO3 solution (20 mL) as the strip-

ping solution.

Miniaturized sample preparation techniques have been

developed with the use of polymeric HFs. Thus, HF-LPME has

been employed for preconcentration of metals and organome-

tallic compounds. For instance, HF-LPME has been used in

combination with electrothermal vaporization (ETV)-ICP-MS

for the determination of ultratrace levels of Cu, Zn, Pd, Cd, Hg,

Pb and Bi in environmental and biological samples.48HFs caused

an enhancement of the extraction efficiency, providing an

appropriate sample clean-up and improved stability of the

extractant phase in comparison with related miniaturized LPME

approaches such as single-drop microextraction.

Surfactants are characterized as being non-volatile, non-

flammable and, in general, as showing negligible toxicity. Several

analytical separation processes have been improved in terms of

greenness by using surfactants as extraction media, cloud point

extraction (CPE) being the most relevant and popular.49 CPE is

based on the formation of a turbid solution when a sample

containing a surfactant is heated over the cloud-point tempera-

ture. Above this temperature, which depends on the type of

surfactant used and its concentration, two immiscible phases are

formed, the surfactant-rich phase being the one capable of

extracting a variety of hydrophobic compounds. Thus, surfac-

tants can be used as green extractant phases in CPE for enriching

target analytes prior to their determination by atomic spectro-

metric techniques, thereby avoiding the use of volatile organic

solvents commonly used in LLE. Several methods for total

element analysis and speciation involving CPE can be found in

the literature.49

On line-CPE avoids the equilibration, cooling and centrifu-

gation procedures typically needed in batch mode, hence

providing an increase in sample throughput. Furthermore, the



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


elution step can be easily performed. Ortega et al.50 employed a

flow injection (FI)-CPE method in combination with inductively

coupled plasma-optical emission spectrometry (ICP-OES) for

the determination of total Gd in previously digested urine

samples. Gd(III) was complexed with 2-(5-bromo-2-pyridylazo)-

5-diethylaminophenol and extracted with the non-ionic

surfactant poly(ethylene glycol) mono-nonylphenyl ether. A

homemade collection column was used to retain the surfactant

rich phase containing the analyte, which was finally eluted with 4

mol L�1 HNO3. Multielemental analysis has also been per-

formed by combination of on-line CPE with ICP-OES. Thus,

Yamini et al.51 performed the on-line preconcentration of Cd(II),

Co(II), Cr(III), Cu(II), Fe(III) and Mn(II) by complexation with 1-

(2-theonyl)-3,3,3-trifluoroacetone and extraction by using a non-

ionic surfactant (Triton X-114).

The use of MW irradiation in combination with surfactant-

based procedures has demonstrated to be highly efficient, thus

allowing an important reduction in the extraction time, incuba-

tion temperature and energy consumption as compared to

conventional hot plate CPE. For instance, Simitchiev et al.52

reported a MW-assisted CPE-ICP-MS method for the determi-

nation of Rh, Pd and Pt in pharmaceuticals. In addition,

Meeravali and Jiang53 determined Au and Tl in soils and water

samples by MW-assisted mixed micelle CPE-ICP-MS.

Recently, surfactants have been applied for extraction of

metals by means of admicelles and hemimicelles adsorbed onto

the surface of metallic nanoparticles. For instance, Faraji et al.54

determined Hg(II) by FI-ICP-OES after SPE of mercury–Mich-

ler’s thioketone complex by means of sodium dodecyl sulphate

(SDS)-coated magnetic nanoparticles. Furthermore, Kar-

atapanis et al.55 employed cetylpyridinium bromide-coated

Fe3O4@SiO2 nanoparticles to extract Cu(II), Ni(II), Co(II), Cd(II),

Pb(II) and Mn(II) as their complexes with 8-hydroxyquinoline,

prior to their determination by ETAAS. Specific features to be

emphasized are the low consumption of surfactant per analysis

(�30 mg), the high enrichment factors achieved and the renew-

ability of magnetite nanoparticles.

Emulsification has been exploited for the extraction of metals

and metalloids in complex samples such as lubricating oils56 or

cosmetics.57 Emulsification of oily samples with surfactants and

water can be considered as a green sample preparation technique

since it avoids the use of organic solvents and the destruction of

the organic phase, mainly performed in the literature by acid

digestion. The formation of water-in-oil emulsions has been

exploited for the development of greener methodologies

compatible with atomic spectrometry. Thus, Aranda et al.58

presented a methodology based on the combination of emulsion

formation and cold vapour (CV)-AFS for total and inorganic Hg

determination in biodiesel samples. In addition, Cassella et al.59

determined Cu, Fe, Ni and Pb by ETAAS in diesel oil samples by

the formation of a water-in-oil emulsion with Triton X-114 in

acidic media and subsequent breaking of the emulsion by

heating.

2.4. Green solvents and reagents

Green chemistry also deals with risk reduction and pollution

prevention. Risk is defined as the product of hazard and expo-

sure.60 Exposure to a given hazardous substance may be reduced,


for instance, by using miniaturized sample preparation tech-

niques. However, exposure controls are capable of failing, then

maximizing the risk when hazardous reagents and solvents are

used. The removal of toxic solvents and reagents from the

analytical procedures is thus a challenging task that has been

faced by researchers, especially in the last two decades. In spite of

being highly desirable, the full removal of certain solvents and

reagents is not always achievable without significant worsening

of the analytical characteristics. In these cases, the replacement

of harmful solvents and reagents by greener alternatives is

advisable. For instance, volatile organic solvents have been

replaced by water,41 ILs,61 supramolecular solvents62 and carbon

dioxide63 in a variety of sample preparation techniques for total

element analysis and speciation, thus giving rise to greener

analytical methodologies. However, toxic organic solvents, such

as benzene64 or chlorinated solvents65 are being systematically

employed in certain sample preparation techniques. In general,

the selection of a given solvent for its application in atomic

spectrometry is performed by comparison of certain physico-

chemical properties, such as solubility, polarity, density, viscosity

or vapour pressure. Given the environmental, health and safety

impact of organic solvents, their toxicological features should be

seriously taken into consideration. Therefore, we should also

consider aspects such as toxicity, flammability, explosivity,

stratospheric ozone depletion and/or atmospheric ozone

production, in order to also fulfil the criterion of reduced

hazards.66 In addition to the impact on health and environment,

the energy required to manufacture the solvent and the cumu-

lative energy demand should also be evaluated for potentially

feasible solvents.67 The use of a solvent selection guide is highly

recommended for the development of green analytical methods,

such as those recently proposed by GlaxoSmithKline (GSK)68

and Pfizer,69 respectively. A quick view of green and less green

solvents commonly used in the industry and analytical labs is

shown in Table 2. Detailed information of the relevant aspects

considered to establish the greenness of organic solvents can also

be found in the literature.70

When reagents cannot be replaced by environmentally friendly

alternatives, their minimization should be considered as a viable

option. Thus, the employment of multicommutation,71,72

sequential injection,73 and lab-on-valve systems,74,75 the immo-

bilization of reagents onto a solid substrate74 or the introduction

of the necessary reagents as part of the extractant phase in

microextraction techniques76 allows an important reduction of

the mass of reagents needed to perform a single analysis and,

therefore, a drastic reduction of costs and wastes produced.

A ‘reagent free’ photo-induced CVG method was reported by

Li et al.77 for the determination of mercury in alcoholic beverages

by exploiting the reducing capacity of the ethanol present in wine

and liquor samples when exposed to UV irradiation.

The development of ligandless analytical procedures combined

with atomic spectrometry has also been reported in the literature.

Thus, formation of metal hydroxides78,79 or insoluble chlorides80

has been employed for the development of ligandless analytical

methodologies by pH adjustment and addition of NaCl,

respectively.

The application of unrefined natural reagents as greener and

cheaper reagents has also been referenced in the literature.81 For

instance, Tuzen et al.82,83 employed SPE resins containing



Table 2 Commonly used solvent selection guides in terms of greenchemistryc

Solvent

Solvent selection guide

GSKa Pfizerb

Water Few issues (greenest option) PreferredHydrocarbonsPentane UndesirableHexane Major issues UndesirableHeptane Some issues Usable2-Methylpentane Major issuesIsooctane Some issues UsableCyclohexane Some issues UsableMethylcyclohexane UsableBenzene Major issues UndesirableToluene Some issues UsableXylenes Usablep-Xylene Some issuesAlcoholsMethanol Some issues PreferredEthanol Some issues Preferred1-Propanol Some issues Preferred2-Propanol Some issues Preferred1-Butanol Few issues Preferred2-Butanol Few issuestert-Butanol Some issues PreferredEthylene glycol Usable2-Methoxyethanol Major issuesHalogenated solventsDichloromethane Major issues UndesirableChloroform Major issues UndesirableCarbon tetrachloride Major issues Undesirable1,2-Dichloroethane Major issues UndesirableKetonesAcetone Some issues PreferredMethyl ethyl ketone Major issues PreferredMethyl isobutyl ketone Some issuesCarboxylic acidsAcetic acid UsableEthersDiethyl ether Major issues UndesirableDiisopropyl ether Major issues Undesirabletert-Butyl methyl ether Some issues UsableCyclopentyl methyl ether Some issues1,2-Dimethoxyethane Major issues Undesirable1,4-Dioxane Major issues UndesirableTetrahydrofuran Major issues Usable2-Methyl tetrahydrofuran Some issues UsableEstersMethyl acetate Some issuesEthyl acetate Some issues PreferredPropyl acetate Few issuesDimethyl acetate UndesirableIsopropyl acetate Few issues Preferredtert-Butyl acetate Few issuesNitrogen-containing solventsAcetonitrile Major issues UsablePyridine UndesirableN-Methyl formamide Major issuesN-Methyl pyrrolidone Major issues UndesirableDimethyl formamide Major issues UndesirableDimethyl acetamide Major issuesSulfur-containing solventsDimethyl sulfoxide Some issues Usable

a Ref. 68. b Ref. 69. c The GSK solvent selection guide establishes threetypes of solvents ranked from the greenest to the least green: few issues> some issues > major issues. In the same way, the Pfizer solventselection guide establishes three types of solvents ranked from thegreenest to the least green: preferred > usable > undesirable.


Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


Bacillus sphaericus and Streptococcus pyogenes for Cr and Hg

speciation, respectively.

Green reagents have also been employed to increase the effi-

ciency of certain analytical processes. Thus, ILs have been used in

combination with complexing agents84,85 to achieve the enhance-

ment in the CVG efficiency of transition and noble metals.

2.5. Green derivatization methods for total element analysis

and speciation

In accordance with the 8th principle of green chemistry, unnec-

essary derivatization should be avoided whenever possible in

order to limit the use of additional reagents that, in turn, can

generate wastes.43 The improvement of analytical methods for

total element analysis and speciation has also been derived from

the application of greener derivatization methods. Thus, several

strategies have been proposed in the literature in order to avoid

conventional derivatization methodologies that involve the use

of non-green reagents and/or the formation of hazardous by-

products.

Conventional methods, such as HG or CV generation, involve

the use of toxic and expensive reagents, namely, tetrahydrobor-

ate(III), tin chloride or potassium permanganate. The replace-

ment of CVG by powerful and greener derivatization alternatives

has been a hot topic in analytical chemistry in recent years.86

Photo-CVG, based on the direct conversion of non-volatile

precursors into volatile species by means of photochemical

reactions, has been studied and employed to the development of

greener alternatives to classical CVG for sample introduction in

analytical atomic spectrometry.11,87–92 The use of low molecular

weight organic acids, alcohols and aldehydes as organic precur-

sors to assist UV reduction allows the formation of volatiles of

analytical interest, being employed for the determination of a

group of elements, including Ba, Fe, Co, Rh, Ni, Pd, Cu, Ag, Au,

Cd, Hg, In, Sn, Pb, As, Sb, Bi, S, Se, Te and I.86

Ultrasound-promoted cold vapour generation has also been

successfully employed for the conversion of Hg(II) into Hg0 in the

presence of formic acid, thus avoiding the use of chemical

reducing agents.93 The mechanism is based on the decomposition

of formic acid by means of US irradiation and subsequent

reduction of Hg(II) to Hg0 by the reducing volatiles generated. It

is interesting to note that reagentless formation of Hg0 is ach-

ieved by sonication of the sample in the absence of any chemical

reagent even though the conversion efficiency is reduced in

comparison with the use of formic acid. This method has been

applied so far to the determination of Hg in waters and

ophthalmic solutions.93–96 It should be highlighted that ultra-

sound-promoted cold vapour generation is not free from inter-

ferences, since the conversion efficiency is affected by oxidants

and complexing agents.

Hydrides can be electrochemically generated, thereby avoiding

the use of sodium tetrahydroborate. Thus, electrochemical

hydride generation (EC-HG) avoids the use of an expensive

chemical reagent that can introduce contamination and is

unstable in aqueous solution. Furthermore, the generation media

for the hydride-forming elements is similar and the efficiency of

HG is not affected by the oxidation state of the analyte.

However, some drawbacks have been attributed to EC-HG,

including limited applicability, significant interferences from



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


concomitant species, e.g., Cu(II) being the most severe one, and

the poor stability of the cathode material.86,97

Dielectric barrier discharge (DBD)-induced CVG has been

recently proposed for Hg determination.98 Cold vapour genera-

tion in the DBD cell was improved by using formic acid 2% (v/v)

as the reaction medium. The mechanism by which Hg0 is formed

may be attributed to the decomposition of water and/or low

weight organic compounds and formation of radicals and

reducing agents by the DBD plasma and UV irradiation. Direct

conversion (by oxidation and atomization) of thiomersal into

Hg0 has been recently demonstrated by using a DBD cell, hence

avoiding pre-treatment steps.99 The authors directly determined

thiomersal in commercial vaccine samples by combining DBD-

plasma induced vaporization with AFS without the need to use

any chemical reagent.

2.6. Advanced oxidation methods

As previously discussed in Section 2.2, conventional sample

preparation methods for organic matter removal prior to trace

element determination involve the use of concentrated mineral

acids and high temperatures. Thus, conventional methods such

as acid digestion and/or mineralization of the sample by dry

ashing are prone to contamination, being furthermore time- and

energy-consuming. Advanced oxidation processes (AOPs) have

been developed in recent years, nowadays being considered as

greener sample preparation techniques in analytical chemistry.

UV-photo-oxidation, ozonolysis and US irradiation, as well as

the combination of these three AOPs, have been exploited for

trace-element analysis and speciation.11,100 AOPs are based on

the use of clean energies and/or chemicals with oxidizing prop-

erties and in situ formation of potent oxidizing radicals, such as

the hydroxyl radical. Relatively low concentrations of well-

known chemical oxidizing agents, such as hydrogen peroxide,

potassium persulfate, or the less green potassium dichromate, are

commonly added to facilitate the oxidation process. AOPs are

used for oxidizing the organic matter of the sample prior to

elemental determination, extraction of analytes from solids

present in an aqueous medium, and for destroying organome-

tallic compounds, thereby allowing speciation analysis.

Among the benefits of AOPs, the reduced amount of chemical

reagents needed can be highlighted, with the subsequent advan-

tages in terms of reduced contamination risks, waste generation

and economy, the possibility of performing the sample pre-

treatment at room temperature, and the low cost of equipment.

In addition, AOPs can be performed on-line.

Fern�andez-Costas et al.101 reported the combination of US-

assisted extraction with ozonation for determination of As in

biological and environmental solid samples by HG-AFS.

Ozonation proved to be highly efficient in the removal of organic

matter prior to the elemental analysis, avoiding foam formation

and, as a consequence, flame instability.

Sonolysis has been proposed as an efficient oxidation method

for the conversion of organomercurials (e.g., methyl-, phenyl-

mercury) into inorganic mercury for the subsequent determina-

tion of total Hg in waters by FI-CV-AAS. Complete oxidation

can be accomplished within 3 min by ultrasound irradiation,

hence avoiding chemical oxidants and strong reaction conditions

(i.e., high temperature and pressure).102


The combined use of focused US irradiation with ozone

(sonozone) was first proposed by Bendicho’s group103 as sample

treatment for determining reactive arsenic toward sodium

tetrahydroborate. Sonozone has been used also for oxidizing

methylmercury into inorganic Hg, aimed at determining inor-

ganic and total Hg in undiluted urine samples by FI-CV-AAS.104

A novel high-efficiency photooxidation (HEPO) reactor was

introduced by Nakazato and Tao for the efficient and expeditive

conversion of organoarsenic species into As(V) prior to the

determination of arsenic species in human urine by liquid chro-

matography (LC)-HEPO-ICP-MS.105 The use of a highly UV

transmitting reaction tube extended within a low-pressure Hg

lamp allowing irradiation at both 185 and 254 nm was key to the

rapid photooxidation of a variety of organoarsenic species. A

photooxidation time of 3.5 s was in fact enough for the efficient

conversion of organoarsenic species without the addition of any

oxidizing agent.

The combination of AOPs with green sample preparation and

derivatization procedures prior to the elemental analysis has

demonstrated to be a powerful alternative for greening analytical

methods. For instance, we reported the use of photooxidation in

the presence of H2O2 (UV/H2O2) of thiomersal (sodium ethyl-

mercurithiosalicylate) in ophthalmic solutions prior to the sono-

induced cold vapour generation technique.96 Thus, the whole

method involves the use of 0.1 mL of H2O2 and 0.35 mL of

HCOOH for degradation of thiomersal and reduction/vapor-

ization, respectively.

2.7. Thermal desorption

Desorption of the analytes once they have been preconcentrated

is generally carried out by liquid or thermal desorption. Organic

solvents and acidic aqueous solutions are commonly used when

combining the preconcentration technique with HPLC and/or

detection by atomic spectrometry. In spite of being convenient

for appropriate desorption of target analytes, the use of such

eluting agents is generally considered as a non-green process,

especially when relatively large volumes are employed and, in

consequence, large volumes of wastes are produced.

Thermal desorption is considered as a greener alternative to

liquid desorption. In fact, the use of a solventless sample prep-

aration technique with thermal desorption provides the greenest

way towards the development of sustainable analytical proce-

dures. Analytes can be thermally desorbed by insertion of the

SPME fiber into the injection port of a gas chromatograph.106,107

Thermal desorption can also be performed after SBSE by using a

modified thermal desorption unit.32

Nevertheless, certain designs have been reported in the litera-

ture that allow the thermal desorption for direct detection by

atomic spectrometric techniques. For instance, we have reported

the combination of headspace (HS)-SPME with quartz furnace

atomic absorption spectrometry (QFAAS) for the determination

of tetraethyllead in gasoline and water samples108 and methyl-

mercury in seafood samples by HG and chloride generation.109 A

variety of volatilizators were tested, the tube-shaped design being

the preferred option due to the higher sensitivity and reproduc-

ibility achieved, presumably as a result of its lower inner volume.

Dietz et al.110 employed a home-made thermal desorption unit

containing a gas chromatographic stationary phase that allowed



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


the separation in less than two minutes of at least two organo-

selenium compounds by coupling SPME with QFAAS and

ICP-MS.

Metallic surfaces have also been employed for adsorption of

target analytes and subsequent thermal desorption. For instance,

Hashemi and Rahimi111 proposed the use of a gold wire for the

preconcentration of mercury by amalgamation and subsequent

determination by ETAAS. Mercury was desorbed at 600 �C by

directly inserting the gold wire in the sample introduction hole of

the ETAAS instrument. Zierhut et al.112 employed active gold

collectors for the preconcentration of mercury species in natural

water samples. Amalgamation allowed the adsorption of Hg0,

while the adsorption of Hg2+ and MeHg+ was attributed to the

catalytic activity of gold nanostructures. Mercury species were

released as Hg0 from the gold collectors by thermal desorption at

550 �C, thus allowing the analysis by AFS. More recently,

Romero et al.113 used a variety of Pd-based collectors (Pd wire,

Pd-coated stainless steel wire and Pd-coated SiO2) for micro-

extraction and preconcentration of mercury. Thermal desorption

of mercury amalgamated onto the Pd wires was performed by

insertion into a modified quartz-T cell for AAS measurement.

Fig. 5 Flow injection systems (a) FIA (flow injection analysis); (b) SIA

(sequential injection analysis); (c) MCFIA (multicommutated flow

injection analysis); (d) MSFIA (multisyringe flow injection analysis); (e)

LOV (lab-on-valve); and (f) LOC (lab-on-a-chip).

3. Flow analysis in atomic spectrometry

Although flow systems have been proposed in order to automate

many analytical methods and improve sample throughput as well

as other analytical characteristics, these systems can also be

considered from the point of view of green chemistry.1 Thus,

according to the first principle, reagent consumption and waste

generation are usually lower than in batch procedures.114 In

agreement with the fifth and the eighth principles, sample treat-

ment can be simpler and faster, thus avoiding the use of auxiliary

reagents and the generation of derivatives.115 On-line monitoring

of processes is also achievable to control and prevent pollu-

tion,116 thus fulfilling the eleventh principle. In addition,

according to the sixth and twelfth principles, automation allows

high sample throughput with lower energy consumption and a

reduction of potential risks to the analyst.

Different flow systems typically used in combination with

atomic spectrometry are shown in Fig. 5. As can be seen, these

systems extend from the FIA introduced by Ruzicka and Hansen

in 1975117 up to more recent flow-based miniaturized systems

such as the lab-on-a-chip.118 The evolution of these systems

shows a clear trend towards an increase in automation and

miniaturization levels. Sample pre-treatment, derivatization,

separation and even waste recycling or in-line waste detoxifica-

tion can be carried out in current flow systems. In addition, these

versatile systems are not particularly expensive.

In this section we consider the possibilities offered by several

flow analysis systems and their role in the development of GAC,

including flow and microflow-injection analysis, sequential

injection analysis, multicommutation, lab-on-valve and micro-

fluidics chips also named as lab-on-a-chip (LOC).

3.1. Flow and microflow-injection analysis

Flow injection systems, based on the injection of a liquid sample

into a moving, non-segmented continuous carrier stream of a

suitable liquid, can be easily coupled to continuous atomic


spectrometric detectors, such as, flame atomic absorption spec-

trometry (FAAS), ICP-OES and ICP-MS. On the contrary, for

discontinuous techniques, such as ETAAS, the coupling of

continuous flow systems is limited. It is possible to achieve a

semi-on-line coupling allowing different interesting approaches,

i.e. on-line sample treatment.119

In the initial stage of development, single-line manifolds with

continuous flow were used. Although this configuration provides

simple procedures and certain grade of automation, it displays an

important drawback from the standpoint of GAC, i.e., reagents

are consumed even when a sample is not processed, thereby

contributing to increased reagent consumption and waste

generation. The use of merging zones with intermittent flow

systems minimized this problem, also improving automation,

sensitivity and precision. This configuration has been mainly

applied in HG or CV. For example, Shao et al.120 developed an

intermittent flow reactor for the determination of total mercury

by AFS. With this configuration, 700 mL sample, ca. 900 mL

reductant (flow rate 4.0 mL min�1 for 14 s) and 1.4 mL carrier

(flow rate 4.0 mL min�1 for 21 s) were consumed per replicate.

Compared to continuous flow systems, this intermittent config-

uration reduces the consumption significantly. For instance,

Vermier et al.121 proposed a procedure based on a continuous

flow system coupled to AFS for mercury determination in bio-

logical samples. The volume of the sample and carrier consumed

was 35 mL (flow rate 7 mL min�1 for 5 min) and that of the

reductant was 15 mL (flow rate 3 mL min�1 for 5 min) per

replicate.

Waste generation remains high in FI systems because they

involve the use of one or more carrier streams to transport the



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


sample and reagents to the detector. So, new designs related to

waste recycling and/or treatments have arisen.122 However, they

are not easy to implement, because usually the waste is highly

diversified, and therefore, there are no general strategies. Thus,

waste recycling has been implemented mainly in procedures

involving solvent extraction and/or analyte preconcentration.

Generally, phase separation is used to recover solvents in order

to reuse them. For instance, a back extraction column has been

proposed for recycling benzene using an automated on-line

solvent extraction for the determination of As and Sn by

ETAAS.123

For on-line waste treatment, different strategies and reagents

are used in order to destroy or passivate the toxic species in the

effluent. Metal ions must be passivized by adding a reagent in the

waste stream. For instance, different trace heavy metals (Cr, Cd,

Ba.) were on-line deactivated by co-precipitation with NaOH

and Fe(OH)3 in a system developed for the determination of Hg

in milk by AFS.71 For the detoxification of degradable wastes,

different strategies have been suggested, such as, thermal

degradation, oxidative detoxification, photodegradation and

biodegradation.4,10

FI systems have allowed automation and acceleration of

different sample treatments such as solvent extraction,124 acid

digestion,120 SPE125 or SPME.126

On-line digestion results in greener procedures than off-line

digestion. In general, lower volumes and concentrations of acids

as well as temperatures and pressures are used. For instance,

Shao et al.120 developed an on-line acid digestion for Hg deter-

mination in mainstream cigarette smoke using 1.4 mL of 4% (v/v)

sulphuric acid. In addition, with on-line digestion, a reduced

exposure of lab staff to potential risks is achieved (e.g., risks from

explosion and emission of vapours).

The use of natural reagents and their immobilization in FI

systems is an interesting alternative for the development of

environmentally friendly procedures. Maquieira et al.127

proposed the on-line preconcentration of heavy metals using

immobilized cyanobacteria as the biosorbent and detection by

FAAS. 20 mg of cyanobacteria were immobilized on controlled

pore glass retaining the activity for 3 months.

Greening FIA by the miniaturization way has been achieved

with micro-FIA systems (mFIA). In atomic spectrometry, mFIA

is mainly coupled with ICP-MS since it can be coupled to

micronebulizers.128–131Therefore, the consumption of sample and

reagents is only a few microliters, and consequently, waste

generation is very low. For instance, the microflow injection

system proposed by Takasaki et al.131 for the determination of

metals in some mice organs consumes only 20 mL of sample with

a flow rate of 10 mL min�1 for 2 minutes.

3.2. Sequential-injection analysis

Sequential injection analysis was developed by Ruzicka et al.132

in 1990 with the aim of overcoming some disadvantages of FIA,

mainly high consumption of samples and reagents and

complexity of the manifolds. SIA has been considered as the

second generation of FIA-based techniques.

The main feature of SIA manifolds is the multiposition selec-

tion valve providing more simple and robust designs. Fluids are

manipulated within the manifold by means of a bi-directional


pump. The process is computer-controlled and both the sampling

sequence and the volume of each aliquot are defined by software.

The sample and reagents are sequentially aspirated. Then, the

volume inserted into the analytical path is only that necessary for

reaction development. Therefore, a drastic reduction in the

consumption of reagents and sample can be achieved, of

the order of 10–20 times in relation to FIA.133 For example, the

consumption of reagents for CV can be reduced 10 times134 in

comparison with FIA methodology based on continuous reagent

addition.135

SIA is especially interesting for complete automation of

sample treatment. Thus, automation of LLE using FIA has some

drawbacks such as low extraction efficiency and limited range of

sample-extractant volume ratios.124 These drawbacks can be

overcome by SIA, because the extraction step takes place on a

thin pseudo-stationary organic film formed on the surface of the

tube. It allows a precise control of sample-to-extractant volume

ratios in a wide range with higher extraction efficiency, lower

reagent consumption and waste generation.136–138

SIA is widely used to automate SPE procedures using atomic

detectors, e.g., Wang and Hansen139 designed an automatic

sequential injection on-line solid phase extraction system for

cadmium determination by ETAAS using a microcolumn packed

with PTFE beads. The sample consumption was 3 mL per

analysis and the analyte was eluted with only 50 mL of ethanol.

After each analysis the microcolumn was washed and regen-

erated with 400 mL of a mixture of ethanol–nitric acid.

Although SIA can be considered as a greener alternative to

FIA, the choice of one or the other depends on the specific

analysis and features associated, such as sampling rate, auto-

mation grade, sample availability and cost and toxicity of

reagents.

3.3. Multicommutation

Multicommutation was developed in 1994 by Reis et al.140 as a

flow-analysis option (multicommutated flow injection analysis,

MCFIA) in order to increase the versatility of flow systems,

reduce reagent consumption, improve mixing and facilitate

automation. Multicommutation is fully computer-controlled and

utilizes multiple solenoid valves as separate switching devices to

create a more flexible flow path that is able to use significantly

less reagents than FIA since they are recirculated to their

containers when not used.141

MCFIA and FIA have recently been compared for the deter-

mination of total Se in infant formulas by HG-AAS.142 Although

the sample consumption is similar in both systems, consumption

of reagents using the multicommutated system is ca. five times

lesser than in FIA. It also provides better detection and quanti-

fication limits with higher sampling frequency (160 samples per

hour with MCFIA vs. 60 samples per hour with FIA).

Multicommutation principles have also been implemented in

modified SIA (multisyringe flow injection analysis, MSFIA).133

Conventional rotatory valves used in SIA are replaced by sole-

noid valves. Although most applications of MSFIA rely on UV-

spectrophotometry detection there are some applications for the

analysis of trace metals by atomic spectrometric detection, such

as AFS143 or ICP-OES.144



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


Like FIA and SIA techniques, multicommutation systems can

incorporate on-line sample treatment. SPE is also the most

popular sample treatment, e.g., Leal et al.143 used a column for

the preconcentration of arsenic prior to the analysis by AFS. The

work demonstrated that MSFIA decreases the consumption of

reagents and sample in comparison with FIA. In addition,

compared with a SIA system, MSFIA with preconcentration

provides higher sample throughput (36 vs. 6 sample h�1) and a

detection limit 22 times better.

In spite of the advantages of MSFIA systems, it should be

noted that most of the published works do not involve treatment

steps, because solenoid pumps do not work properly under

backpressure, thus, when a sample treatment step is coupled to

the system, the sample throughput can decrease considerably.

Following the trends towards cost-effective procedures, with

lower reagent and sample consumption and waste generation as

well as fast analysis, the use of multipumping flow systems

(MPFSs) has been proposed.145 These systems are based on the

combined use of solenoid valves and pumps operated in the form

of pulses. The number of pulses defines the total injected volume,

while the frequency of pulses defines the liquid flow-rate. MPFSs

have been used for trace metal determination by atomic spec-

trometry.146–148 For example, P�erez-Sirvent et al.147 determined

Hg by AFS. When the MPFS-based procedure is compared with

conventional flow systems,135 a substantial improvement in

sample throughput is obtained (82 samples per hour, instead of

30 samples per hour with conventional peristaltic pumps). In

addition, 90% of reagent volume and 95% of sample volume are

preserved, so waste generation is considerably diminished.

3.4. Lab-on-valve

Lab-on-valve was introduced by Ruzicka149 in 2000, and has

been accepted as the third-generation of FIA. LOV has been

developed by implementation of SIA principles in a modified

system where all components are integrated on a six-port selec-

tion valve. LOV systems involve significant progress in minia-

turization, automation and integration of on-line sample

treatments. Hence, reagent consumption and effluent generation

have been drastically reduced.

LOV has been coupled with different atomic spectrometry

techniques for the determination of metal species. For instance,

CV in a LOV system has been applied for Hg determination by

AFS.150 With this configuration the sample and reagent

consumption is only 500 mL and 400 mL respectively. Also, they

achieved a high sample throughput, i.e., 90 samples per hour.

The low sample and reagent consumption, as well as low waste

generation, makes these systems suitable for achieving greener

analytical approaches.

LOV is used to automate sample treatment, e.g., SPE. There

are two strategies for performing SPE, namely, packing the solid

material in a micro-column and using the so-called bead-injec-

tion (BI) principle. The latter option is widely used in LOV

platforms for routine analysis because it avoids the main prob-

lems associated with conventional on-line column preconcen-

tration systems, such as high backpressure or deactivation of the

surface of the solid material. In LOV-BI, a micro-column is

generated in situ by aspiration of the beads. Usually, the solid

material is renewed after each analytical cycle. This is the main


drawback of this strategy from a standpoint of GAC. In spite of

this, when the combination of LOV-BI and ETAAS is used, trace

metals can be determined without analyte elution since beads are

transferred into the graphite furnace, e.g., Ampan et al.151

developed a LOV-BI procedure for the determination of lead by

ETAAS with Sephadex G-25 impregnated with dithizone. It

must be emphasized that the lifetime of graphite tubes is short

due to the residues deposited onto the graphite tubes after

pyrolysis of the beads.

3.5. Lab-on-a-chip

Since the introduction of flow analysis in the 70s, the clearest

trend in its evolution is without doubt miniaturization. In this

sense, Manz et al.152 developed in 1990 the concept of micro-total

analytical systems. This analytical concept has led to the devel-

opment of the so-called lab-on-a-chip devices, allowing a high

miniaturization of the analytical systems.

LOC devices have been an active subject of research in the last

decade.153 The interest in these devices arises from the incorpo-

ration of sample processing steps onto a small chip, thus reducing

the required sample volumes, reagent consumption, waste

generation and time required for the analysis. Also, these

microfluidics systems can enhance the portability compared to

traditional instrumentation and they can be fabricated in a

cheaper way.

Microfluidic chips are constituted by micrometer-scale chan-

nels and reservoirs in a substrate material (usually silica, quartz

or plastic). Although the chip material depends on the applica-

tion, plastic is the most employed today because it is the

cheapest. Three different propulsion mechanisms are used in

LOC devices: electroosmotic flow, hydrodynamic and

centrifugal.154

Chips have been mainly used for metal determination by ICP-

MS.155–157 A microchip-based nanolitre sample introducing

system for ICP-MS allows designing greener procedures than

conventional sampling systems. For instance, Cheng et al.157

developed a microfluidic chip with hydrodynamic flow (20 mL

min�1) for the determination of cisplatin in human serum. With

this system the sample consumption is very low, only 1.8 nL are

needed per analysis, ca. 105 times less than that of the conven-

tional sampling systems. Also, a high sample throughput up to

112 samples per hour was achieved.

As with LOV systems, in LOC devices, different units for

sample treatment can be implemented.158–160 As an example,

Chen et al.159 developed a microfluidic device for magnetic

nanoparticle solid phase microextraction (MSPME). It was

applied to the determination of Cd, Pb and Hg by electrothermal

vaporization-inductively coupled plasma mass spectrometry

(ETV-ICP-MS). For the preparation of the magnetic solid phase

column on the chip, 25 mg of the solid phase were aspired and

introduced into the magnetic zone. The magnetic nanoparticles

were used almost 12 times. Sample consumption was 500 mL per

analysis which is lower than that required with conventional

procedures involving ETV-ICP-MS.

The use of microfluidic chips allows a great miniaturization of

the systems, in addition to a complete automation of the

procedure. The main disadvantage of LOC devices is that they

are systems of fixed structure, and therefore, it is necessary to



Table

3Comparisonofthegreennessprofile

ofdifferentapproaches

forsolidsampling

Electrothermalvaporization/

atomization

Arc/spark

ablation

Laserablation

Glow

discharge

X-ray

Considered

techniques

ETAAS

Arc/spark-O

ES

LA-ICP-O

ES

GD-O

ES

m-X

RF

ETV-ICP-O

ES

Arc/spark-ICP-O

ES

LA-ICP-M

SGD-M

STXRF

ETV-ICP-M

SIC

P-M

SLIB

SEDXRF

WDXRF

Multielemental

capability

ETAAS/N

oYes

Yes

Yes

Yes

ETV-ICP-O

ES/Y

esETV-ICP-M

S/Y

esSample

quantity

0.1–1mga

1–10mga

0.25ng–2mgb

quasinon-destructive

10–100mga

Non-destructive

0.1

mg–500mgc

Usualsample

pretreatm

ent

Homogenization

No

No(LAM)

No

No

Tem

perature–

pressure

conditions

ETAAS/tem

perature

program

(upto

3000

� C)

inanAratm

osphere

Highpotential

difference

between

theelectrodes

inanAr

atm

osphere

10–100mJb

Highpotential

difference

inaninert

gasatm

osphere(usually

Ar)

atreducedor

atm

ospheric

pressure

Ambienttemperature.

Atm

ospheric

pressure

orvacuum

ETV-ICP/(upto

10000

� C),

transport

byanArflow

Portability

No

Yes

LA/ICP-O

ES/N

oNo

m-X

RF/Y

esLA/ICP-M

S/N

oTXRF/Sem

i-portable

LIB

S/Y

esEDXRF/Y

esWDXRF/N

oAutomation

Yes

aYes

aNoa

Noa

Certain

grade

ofautomation(sample

changer

motorized)

Sample

throughput

ETAAS/15min

per

analyte

a1–2min

per

samplea

2–5min

per

samplea

10min

per

samplea

4–120samplesper

hourc

ETV-ICP-M

S/15min

per

samplea

aRef.181.bRef.169.cRef.182.

This journal is ª The Royal Society of Chemistry 2012 J. Anal. At. Spectrom., 2012, 27, 1831–1857 | 1843

Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


design specific chips for each application, hence being less

versatile than LOV systems.

4. Solid sampling by atomic spectrometry

Sample preparation typically consumes reagents, solvents,

energy and is generally labour-intensive. So, it is not surprising

that one of the paradigms of GAC is the elimination of this stage.

The ideal analytical method from the point of view of GAC is

based on direct measurements without sampling, transport,

addition of reagents and waste generation. In this sense, remote

and on-site measurements can be considered the best strategies to

approach the philosophy of GAC.3 This is not always possible,

and therefore, when a sample is analysed in the lab, replacement

of traditional ‘wet chemistry’ for sample pre-treatment is

considered an important goal.2 In fact, developments made in

order to introduce solid samples directly into analytical instru-

ments have been long pursued by analytical researchers.

Sample decomposition by acid digestion is common when

atomic spectrometric techniques are used. It implies the appli-

cation of concentrated acids and high temperatures and pres-

sures. Nowadays, microwave energy operating with closed

vessels involves an efficient way of saving energy and acids. In

spite of this, it continues to be difficult to meet the GAC prin-

ciples when acid digestion is involved. Therefore, solid sample

analysis without or with minimal sample pre-treatment should be

an interesting alternative. This includes direct solid sampling and

slurry sampling (a suspension of a finely powdered sample).

Atomic spectrometry techniques can resort to different

systems in order to cope with solid samples, such as electro-

thermal vaporization, arc/spark ablation, laser ablation (LA) or

glow discharge (GD) sources. It is important to lay emphasis on

those atomic spectrometric techniques that allow performing

green analysis in a non-destructive way due to their ability to

directly analyse solid samples such as X-ray fluorescence tech-

niques. Solid sampling using different atomic spectrometric

techniques has been thoroughly reviewed, which points out the

interest in this topic.161–180 Table 3 shows some characteristics in

order to compare the greenness of different atomic spectrome-

tries using solid sampling.181,182

The advantages of solid sampling from the perspective of GAC

over acid digestion or other sample pre-treatments (e.g., dry

ashing, fusion) can be summarized as follows.

(a) It avoids the use of corrosive and hazardous chemicals.

(b) It reduces energy consumption by elimination of heating.

(c) It minimizes waste generation.

(d) It reduces the exposure of laboratory staff to acid vapours

and improves lab safety.

(e) It reduces labour and improves sample throughput.

(f) It is possible to analyse a very small sample mass [i.e.,

analysis at micro- (10�2 to 10�3 g), submicro- (10�3 to 10�4 g) or

even ultramicro-scale (<10�4 g)].183

Solid sampling can be considered especially green for samples

that are difficult to digest even with very drastic conditions, and

for elements whose levels are usually very low. For instance, Qi

et al.184 have recently reported a digestion method for determi-

nation of the platinum group elements in geological samples by

ICP-MS. Due to their chemical characteristics and low concen-

tration, both laborious and tedious dissolution procedures are


required. Thus, between 2 and 10 g of the sample are first

digested with 15–30 mL of HF in a PTFE beaker on a hot plate to

remove silicates up to dryness. The residue is then digested with 5

mL of HF + 15 mL of HNO3 at 190�C for about 24–48 h in a

stainless steel pressure bomb. After cooling, 2 mL of HCl are

added and evaporated to dryness on a hot plate. In order to

remove most of the residual acids, 5 mL of concentrated HCl are

added to the bomb. After drying, the residue is dissolved with

40 mL of 2 N HCl. The resultant solution is then decanted to a

50 mL tube for centrifuging at 2800 rpm for 5 min. The upper

portion is used to preconcentrate platinum group elements by

coprecipitation. The precipitate is dissolved with aqua regia, the

solution is evaporated to near dryness, redissolved again with 0.3

mL of aqua regia and diluted to 10 mL. An ion exchange resin is

necessary to remove some interfering elements, such as Cu, Ni,

Zr and Hf.

The last procedure can be compared with solid sampling by

laser ablation and ICP-MS. For instance, Boulyga and Heu-

mann185 suspended 1 g of sample in 0.2–5 mL of different

isotope spike solutions. This suspension is dried at 75 �C,homogenized by mixing with a Teflon pestle and pressed into

pellets for direct laser ablation. 3 mg of a rock sample are

ablated within one analytical run (1 min ablation time). 50–67

successive runs are performed for each rock sample. Undoubt-

edly, solid sampling provides clear advantages with regard to

the digestion procedure: it eliminates the use of HF, HNO3 and

HCl; it reduces steps, time and labour and reduces the

temperature of operation (190 vs. 75 �C).

4.1. Electrothermal vaporization/atomization for solid

sampling

Trace metals can be directly vaporized and atomized from a solid

sample introduced into an electrothermal atomizer/vaporizer,

e.g., graphite furnace. It is an interesting alternative to sample

dissolution in AAS, ICP-OES and ICP-MS. Although direct

solid insertion (DSI) into a flame or plasma is somehow possible,

ETV systems have successfully extended solid sampling to ICP-

OES and ICP-MS. The latter approach provides matrix removal

during the pyrolysis step, for which it can be considered as a

thermochemical reactor allowing in situ sample treatment.165

From 1971, the year in which the first application of solid

sampling by ETAAS with a commercial atomizer was pub-

lished,186 until today, important progress regarding instrumen-

tation for solid sampling has been achieved. Spectrometers

equipped with autosamplers that allow weighing, introduction of

the solid sample automatically and calibration with aqueous

standards as well as the addition of a matrix modifier are now

commercially available (e.g., SSA 600L-fully automated solid

sampler with a liquid dosing unit and up to 84 samples from

Analytik Jena).187

Although ETV was used for the first time in 1974,188 applica-

tions of solid sampling with this system were performed much

later. Probably, this fact can be associated with the commer-

cialization of more robust ETVs at the end of the 90s. A degree of

automation analogous to ETAAS can be achieved with ETV

systems. An autosampler and a microbalance can be coupled to

an ETV-unit for solid sampling by ICP-OES or ICP-MS (e.g.,

autosampler AWD-50 from Spectral Systems Advanced



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


Technologies).189 The main green advantage of ETV-ICP-OES

and ETV-ICP-MS with respect to ETAAS for solid sampling is

their multielemental capability.

In spite of that, solid sampling with these atomic spectrometric

techniques is unusual in routine labs. Though the state-of-the-art

of the instrumentation has eliminated the difficulties related with

the insertion of the solid sample into the atomizer, i.e., the risk of

sample losses and contamination during the weighing and

transfer from the balance to the atomizer,161 important analytical

problems (e.g., precision continues to be worse than for liquid

samples and calibration with certified reference materials is still

the most reliable approach, the use of aqueous standards and the

standard addition method being only possible sometimes) and

drawbacks from the viewpoint of GAC continue to be present.

(a) Chemical modifiers interact less effectively with the analyte

occluded within the sample matrix, and hence, a higher quantity

is used in comparison with liquid samples.

(b) Additional reagents may be needed (e.g., hydrogen,

methane or oxygen in the ashing step) in order to remove

interferences.

(c) Higher atomization temperatures are required to release the

analyte in comparison with liquid samples, especially when

refractory elements are determined.

(d) Deterioration of the atomizer is a critical issue and addi-

tional cleaning-out steps can be necessary.

The expertise of the analyst is the key in the success of solid

sampling. Paradoxically, the labour increases, especially along

method development, validation and control. Every analyte and

matrix requires a complete evaluation, i.e., optimization of the

temperature program, matrix chemical modifier, establishment

of a suitable mass interval, etc. This is especially remarkable for

ETV-ICP-MS due to the large number of potential matrix

interferences. Data treatment is also relevant because outliers

frequently appear. So, in order to minimize their influence, the

number of replicates required in solid sampling is higher.190

On the other hand, the corrosion of the graphite atomizer has

been reported by Ortner et al.191 as ‘often disastrous in solid

sampling into graphite boats’ and it can be considered an

important disadvantage in GAC. In addition, release of gaseous

and aerosol products from the matrix is enhanced in solid

sampling. A series of relatively simple strategies such as the use of

modifiers and coatings in graphite atomizers can be used in order

to avoid this problem, i.e., the lifetime of carbide-modified

graphite atomizers is longer than that of standard graphite tubes

for solid sampling.191 The design of alternative atomizers for

solid sampling still continues, e.g., a recent model of an atomizer

named ‘crucible with separated zones’.192 It consists of a graphite

tube placed in the atomization zone and heated independently of

the evaporation zone so that the filtration of sample vapours

through porous walls takes place.

Tungsten based atomizers, mainly W-tubes, have been

proposed as an alternative to graphite furnaces for solid

sampling, especially for slurry sampling. Green characteristics

such as simplicity, low cost and low power requirements have

been achieved with these atomizers. Tungsten is available at low

cost, heating rates are high and a simple power supply is suffi-

cient. In addition, no water circulating system is required as a

coolant. Hou and Jones have reviewed these atomizers in

analytical atomic spectrometry, including their potential in


ETAAS, ETV-ICP-OES and ETV-ICP-MS with slurry

sampling.193 However, not everything is green in this type of

atomizers. These are usually purged with up to 10% of hydrogen

mixed with argon and have a relatively short life.194

Although sample pre-treatment should be avoided whenever

possible in order to retain the green advantages of solid

sampling, it is not always possible. Drying and grinding up to a

suitable particle size are usually performed to improve precision.

In those cases, slurry sampling can be considered more advan-

tageous since it shares the advantages of direct solid sampling

(minimum sample pre-treatment) and liquid sampling (better

precision, introduction with a conventional autosampler, cali-

bration with an aqueous standard, efficiency of chemical modi-

fiers, temperature programs and atomizer corrosion similar to

liquid samples). Therefore, slurry sampling is more suitable for

routine analysis than direct solid analysis.190

Miniaturization, automation and acceleration can be simul-

taneously achieved with slurry sampling (SS). For preparing

slurries, a few milligrams of the powdered sample (typically 10–

20 mg) and a volume of the liquid diluent in the range of 1–

1.5 mL are added into an autosampler cup. In general, this liquid

medium consists of a diluted solution of nitric acid (e.g., 3% v/v)

and, in some cases, a very small amount of a stabilizing agent

such as Triton X-100 or glycerol. Homogenization of the slurry is

critical and, probably, this is the weakest point of the slurry

technique from the perspective of GAC. Although it can be

carried out by magnetic stirring, ultrasound agitation can be

certainly considered as a greener option. In contrast to direct

solid sampling, additional equipment only for the ultrasonic

homogenization of the slurry is required. In this sense,

commercial systems developed in the 90’s incorporate an ultra-

sonic probe into the ETAAS autosampler for automating the

procedure, i.e., USS-100 Ultrasonic Slurry Sampler from Perkin-

Elmer. Only a few seconds of application of this energy is suffi-

cient in order to obtain a homogeneous slurry.

SS can be used with ETV for multielemental determinations by

ICP-MS and ICP-OES. For instance, Lin and Jiang194 used

ultrasonic slurry sampling (USS)-ETV-ICP-MS for determining

Cr, Mo, Pd, Cd, Pt and Pb in drug tablets. Amberger and

Broekaert195 proposed the direct determination of trace elements

in boron carbide powders by SS-ETV-ICP-OES. Slurries can be

also nebulized directly into flames and plasmas. A comparison of

SS-ETV and slurry nebulization (SN) for determination of trace

impurities in titanium dioxide powder by ICP-MS has been

carried out by Xiang et al.196 In both cases, the particle size is

critical, though SS-ETV-ICP-MS has a lower particle size effect

compared to SN-ICP-MS (particle diameter <50 vs. 1 mm

respectively). Then, it is necessary to consider the increased

operation time that reduction of particle size implies.

4.2. Arc/spark ablation

Arc/spark optical emission spectrometry has been used since long

for direct analysis of solid samples. Ablation is carried out by an

electrical discharge between an electrode and the conducting

sample. In spite of the remarkable features (e.g., a multielemental

determination could be performed in ca. 30 s), this classical

technique has not garnered interest as an investigation topic due

to the availability of more advanced techniques such as ICP-OES



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


or ICP-MS, with better analytical characteristics for liquid

sampling but with more difficulties as regards solid sampling.197

In 99% of cases, this technique is used in routine labs of the

metallurgical industry. The remaining 1% corresponds mainly to

the analysis of refractories, precious metals, steel-making slags

and geological materials.198 These last samples must be powdered

and mixed with high purity graphite, which diminishes the scope

of green chemistry.

Some technological advances incorporated into instruments

can be considered as decisive in order to green this routine

technique. Nowadays, more compact and lower-cost instruments

requiring little maintenance can be acquired. In particular, this

has been achieved with the incorporation of charge-coupled

devices (CCD), gas-filled vacuum ultraviolet (VUV) optical

chambers, digitally controlled arc/spark excitation sources,

advanced electronic time-resolved spectroscopy (TRS), fiber

optics and multiple optical cells.197 Portable systems for a variety

of applications including routine sorting, positive material

identification (PMI) or metal certification can be commercially

obtained.199 New developments according to GAC principles

have been recently patented, e.g., in order to conserve argon200 or

to use low current spark generators.201

Today arc/spark ablation can be used for sample introduction

in ICP-OES and ICP-MS, although its use is limited in

comparison with lasers or glow discharge sources. A commercial

spark ablation accessory known as ‘Separate Sampling and

Excitation Accessory (SSEA)’ is used for this purpose. It

improves the analytical characteristics of arc/spark spectroscopy

and allows extending the solid sampling capability to routine

laboratories.202–204 Both cost and maintenance are lower as

compared to other systems such as laser ablation.

4.3. Laser ablation

Laser ablation is a powerful tool for solid sampling that has been

increasingly applied in several fields. In contrast to arc/spark

ablation, laser ablation has greater versatility. All types of

materials can be used for laser ablation, i.e., conducting and non-

conducting, organic and inorganic samples. In addition, LA can

be used as a spatial and depth-resolved high resolution sampling

technique.169 Very small amounts of samples, in the order of ng

or even pg, can be analysed using laser ablation microprobes

(LAMs). So it can be considered as an essentially non-destructive

or minimally destructive technique from the viewpoint of GAC.3

LA systems can be used as sampling and excitation sources

(e.g., laser induced breakdown spectroscopy, LIBS) and coupled

with ICP (LA-ICP-OES and, in particular, LA-ICP-MS). This

last technique combines the green advantages of solid sampling

discussed above with multielemental and isotopic analysis

capability and high sensitivity. The sample is ablated in an

airtight cell and the formed aerosol is carried in a continuous

flow of an inert gas to the ICP where it is excited and ionized for

quantification by MS.169 In the case of LIBS, the plasma plume

generated on the sample surface is used for optical emission

measurements. Incident laser light and emission lines are

resolved both spectrally and temporally. The instrumentation is

simple and includes an ablation laser, an optic collection system,

a monochromator or an echelle spectrometer and a multi-

element photodiode array (typically a CCD).171 In spite of the


good characteristics of LA for solid sampling, matrix effects

must be considered in all cases.

The formed aerosol by ablation of the sample depends not

only on the sample but also on laser characteristics. First, lasers

of ruby and later lasers of neodymium:yttrium aluminium garnet

(Nd:YAG) and excimer lasers have been used for LA. There is a

relationship between laser wavelength, laser irradiance, optical

penetration depth, particle size, and analytical precision and

accuracy. In general, it is accepted that shorter UV wavelengths

improve ablation characteristics in respect to infrared and visible

wavelengths, especially for highly transparent samples. Both,

excimer and Nd:YAG lasers can produce UV light pulses. In

general, excimer lasers offer the shortest wavelength and a

precise sampling due to their spatial coherence. In contrast,

Nd:YAG lasers are simpler, more cost-effective, require little

maintenance and produce higher repetition rates.205

LA procedures can be divided according to the mass sample

and analysis goal into bulk sample analysis and microprobe

analysis. In bulk sample analysis, there is a large amount of

sample and the difficulty lies in obtaining a representative anal-

ysis. The spot diameter is generally >100 mm corresponding to

2 mg–2 mg of ablated mass and then, in many cases, samples must

be homogenized.169 Pulverization and even fusion to form a glass

might be necessary. For instance, a meta-tetraborate fusion

procedure was used with powdered rock by Leite et al.206 in LA-

ICP-MS. Obviously, when a fusion procedure is necessary, the

green advantages of LA are clearly diminished. Therefore,

homogeneous materials such as alloys retain all the advantages

of analysis by LA from the point of view of GAC.

LAM is especially interesting for applications where a spatial

resolution is necessary (lateral and in-depth in the low-mm and

nm range, respectively), i.e., microanalysis, in-depth profiling,

and surface mapping.175 Though LAMs can reduce sensitivity

since a small amount of sample is ablated, it can be considered a

green tool. The spot diameter is generally <100 mm corre-

sponding to 0.25 ng–2 mg of ablated mass. Pulsed laser energy

used in LAMs is small (few mJ) compared with that used for bulk

sampling (10–100 mJ).169 Usually, excimer lasers with short UV

wavelengths are used. Shorter pulses improve LA localization; in

particular ultra-short laser pulses (<1 ps) and more concretely

femtosecond lasers are applied in order to improve the analytical

characteristics.175

LAMs may require sample treatment only in some cases, for

instance, for bioimaging of elements in biological tissues by LA-

ICP-MS. Soft tissues are paraffin-embedded or frozen, then

samples are sliced (usual thickness: 20–200 mm) and deposited on

a glass slide. Both the thickness of the tissue and the laser

parameters should be optimized. Cooled laser ablation cells are

preferably used for this purpose.207 Usually, soft biological

tissues are easy to ablate from a glass substrate and then, a

Nd:YAG laser with a wavelength of 266 nm is sufficient to obtain

highly spatially resolved images.208

In regard to LIBS, green intrinsic characteristics can be iden-

tified in this technique, since in situ analysis and remote sensing

with no sample preparation are suitable. Fieldable laser-induced

breakdown spectrometers have been developed in recent years.

Fortes and Laserna209 have recently revised trends and applica-

tions with these instruments. Portable, remote and stand-off

spectrometers are considered. In general, portability requires



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


compact lasers with portable power supply and miniaturized

spectrometers. Usually, Nd:YAG lasers are used due to size

requirements, reliability and ruggedness. A calibration procedure

without standard reference materials and based on the calcula-

tion of temperature and the electron density in the plasma

(calibration-free) can be used with portable LIBS.210 Spectral

libraries and different data processing algorithms can improve

the green characteristics of LIBS for field measurements. In

addition, automation of portable instruments is possible. A fully

automated portable LIBS instrument has been developed by

Palanco et al.211 When a fiber optic cable is used in a LIBS

system, stand-off (both the laser and the signal are transmitted

along an open path configuration) and remote (laser and/or the

signal are transmitted through a fiber optic cable) analyses of

samples for long distances can be made. It has allowed extending

LIBS application to areas contaminated by toxic or radioactive

materials without danger to the analyst. Very interesting infor-

mation about applications of these systems can be found in the

above-mentioned review.209

4.4. Glow discharge sources

Glow discharge sources with optical emission spectrometry

(OES) or mass spectrometry (MS) are considered powerful and

versatile for bulk, surface and interface analysis of different types

of materials.177 Nowadays, GDs have gained interest due to the

development of radio frequency (rf) sources, since it has allowed

extending its application to non-conductive samples such as

organic coatings, glasses, ceramics, etc. Although with very

similar performance in both depth resolution and sensitivity,

direct current (dc) sources continue to be used most frequently,

only conducting materials can be analyzed.212

In a Grimm-type GD, sputtering is used to generate atoms and

ions directly from the solid sample surface ‘layer by layer’. Low-

pressure plasmas are initiated by applying a high potential (kV)

between two electrodes, one of which is formed by the sample

(usually the cathode). Electrons and positive ions from a

discharge gas (e.g., Ar or mixtures of Ar with N2, O2, H2 or He)

are accelerated towards the cathode surface and when these have

sufficient energy, result in releasing the material (sputtering

process). This process depends strongly on the sample material

and its surface properties. On the contrary, atomization, exci-

tation and ionization processes (separated in space and time of

the sputtering process) are practically independent of the surface

sample.176 For this reason, little matrix effects have been

observed and quantification by MS or OES is usually simpler

than in other techniques for solid sampling.212 Without doubt,

this question can be considered interesting in order to achieve

greener procedures.

New developments in instrumentation have been decisive in

order to extend the application of this technique and improve

both its green and analytical characteristics. In particular, efforts

have been focused on the design of new GDs, but also on

improvements of vacuum technology and interface and on the

implementation of CCDs and ToF (time-of-flight) detectors for

OES and MS, respectively, in order to acquire spectra faster.177

For instance, pulsed rf/dc GDs have represented an important

advance in trace analysis since they allow separating elemental

and molecular excitations. This mode provides high


instantaneous power, increasing the atomization, excitation, and

ionization processes without thermal sample degradation.

Numerous applications (e.g., polymers) are now possible with

these sources.171,213 Magnetically boosted GD sources that

incorporate a magnetic field to improve sputtering rates and

ionization/excitation efficiencies have been also proposed.213,214

Atmospheric sampling GDs with untreated atmospheric gases

were firstly introduced as an ionization source for organic

compounds, though it has been also used for metal determina-

tion.215 The miniaturization of GD sources has also been

considered, although it has been used so far for liquid and gas

samples. A small glow discharge electron source has been used

for miniaturized mass spectrometers.216 Low power require-

ments, mechanical ruggedness, and quality of the data produced

make these sources suitable with a portable handheld mass

spectrometer.

Solid sampling with GDs is not without problems. Non-flat

samples (e.g., screws and tubes) cannot directly be mounted on a

GD and special accessories are required. Porous samples (e.g.,

foams and certain ceramics) are also difficult to handle because

they are not vacuum tight since usually the sample seals the

source.212 Particulate solids can be analysed using rf-GD-OES.

For this, sol–gel thin films or glasses are synthesized by acid-

catalysed condensation. Slurries of powdered samples are

incorporated into the films and analysed for both main and trace

element components.217,218

GD-OES and GD-MS can be compared with other techniques

used for surface analysis, such as SIMS (secondary ion mass

spectrometry) and SEM (scanning electron microscopy with X-

ray analysis). GD-OES and GD-MS are considered cheaper,

faster and easier for quantification than SIMS, and faster and

with better depth resolution than SEM. For bulk analysis, GD-

OES can compete with spark/arc emission and with X-ray

techniques.3,212 Obviously, GD-OES and GD-MS have some

drawbacks such as limited lateral resolution and inability for

micro-spot analysis. Recently, the LA-GD combination has been

proposed for solid sampling. Laser ablates the sample and GD

ionizes the ablated aerosol.219,220

4.5. X-ray fluorescence spectrometry

X-ray fluorescence spectrometry (XRF) can be considered as a

quantitative and qualitative analytical tool that can fulfil GAC

principles. Different techniques are available: wavelength

dispersive X-ray fluorescence (WDXRF), energy dispersive X-

ray fluorescence (EDXRF), total reflection X-ray fluorescence

(TXRF) and micro-X-ray fluorescence (m-XRF). All offer fast

and non-destructive analysis using clean procedures that can

routinely be applied to solid samples. In general, analysis can be

carried out within a time in the range of 30–1000 s with a good

precision.221–224

In spite of this, it is not usual to consider XRF as a set of green

techniques due to risks that this energy involves. The X-ray beam

can be generated with a ceramic tube or from radionuclides.225,226

Radionuclides are more dangerous for the analyst because they

generate g rays, are always ‘‘switch on’’ and have shorter life-

times. Their use is subject to strict regulations and can only be

handled by authorized personnel.227 X-ray tubes are mostly used

in the analytical instrument since they are safe. In addition,



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


miniature X-ray tubes have made possible the development of

portable instruments for in situ analysis. This can contribute to

change the negative perspective on these techniques from the

GAC standpoint.

Although X-ray instruments could potentially be dangerous,

current instruments pose few risks to users when used properly.

Themanufacture and use ofX-ray instruments is highly regulated.

In fact, the design of the instruments limits even accidental expo-

sure. Spectrometers have a lead shielded, closed design that avoids

the scattering of the X-ray beam. In addition, the surrounding of

the equipment should be frequently checked to ensure that there is

no scattering of the X-ray radiation and there is no potential risk

for the analyst by radiation exposure (the maximum permissible

whole-body dose from occupational exposure is 5 ‘Roentgen

Equivalent Man, REM’, per year. When portable equipments are

used, wearing heavy gloves is advisable.228

The main green advantage of XRF is without doubt its ability

for direct analysis of the sample without sample treatment or

with a little preparation such as grinding, cutting, etc. Bulk

materials can be layered with a thickness #0.5 mm by cutting,

sawing or shredding.229For samples such as metals or ceramics, it

is necessary to polish for creating a smooth and clean surface

when WDRXF is used. Grinding to grain sizes of lower than

75 mm is used to obtain a homogeneous powder. Then, for higher

density solids only a pressing step is necessary in most XRF

techniques. For low-density solids, the addition of a binding

agent is needed before pressing to obtain a stable and homoge-

neous pellet. Natural substances such as starch, wax or cellulose

can be used for this purpose being desirable for GAC in contrast

to others such as polyvinyl.230

These non-destructive techniques can be used directly even

with fresh samples. The fresh sample is homogenized and frozen

and then, a portion is pressed into a pellet and analysed. For

instance, the elemental content of the edible part of lobsters has

been established by EDXRF.231

When the sample available is very small, fusion is often used as

the sample treatment in EDXRF and WDXRF.232 Usually,

borate is used as the fusion reagent (above 1000 �C). Fusion melt

is a homogeneous glass with a defined matrix.

TXRF allows analysis of powdered samples without pressing

or forming pellets, only placing on a cleaned carrier, usually

quartz glass. Different strategies can be used with powdered

samples in this technique. For example, a cotton-wool tip has

been used for analysing inorganic pigments in oil paintings. For

sampling, the surface of oil paintings is wiped off by means of a

cotton-wool tip. A few micrograms of the cotton-wool tip are

sufficient for the analysis.233 Recently, the use of slurry sampling

has been proposed in TXRF. For example, biological samples224

using an ultrasonic probe for slurry homogenization have been

analysed. A 10 mL aliquot of the slurry is deposited onto the

quartz glass carrier.

m-XRF has been developed very rapidly in the last decade,

mainly due to its versatility. It uses rotatory X-ray tubes which

provide synchrotron radiation, resulting in a very sensitive

technique with limits of detection (LODs) at the ppt level.178 Not

only is the elemental composition of a sample easy to obtain, but

also the related spatial distribution without sample treatment.

Commercial portable equipments (e.g., ARTAX� equipment

from Bruker)234 are available. They allow in situ measurements


within 30–60 s, and then, sampling and transport to the lab are

not necessary. Portable systems are mainly applied for arche-

ometry and restoration since they avoid contact and damage,

whatever the objects under investigation.235

TXRF can be applied to micro, trace, and surface analyses.

This technique can provide detection limits at the part per billion

level.236 Commercially available TXRF instruments (e.g., S2

Picofox� from Bruker)237 are considered semi-portable systems.

This technique does not need inert gases and/or a vacuum

system. Certain grade of automation can be reached using a

motorized sample changer.

EDXRF is widely used for the determination of major, minor

and trace elements (LODs at ppm level).180 An increased auto-

mation level as in TXRF is reached by using an automatic sample

changer. Commercial portable EDXRF instruments are air-

cooled systems and they can operate in vacuum or in air (e.g.,

Tracer� family from Bruker).238 This equipment has been mainly

designed for in situ measurements in art, archeometry, geological

research, environment and also for specific industrial applications,

i.e., sorting scrap, alloy analysis and sorting for alloy verification.

The use of this portable equipment can have some drawbacks since

instruments are less robust and quantitative analysis can be trou-

blesome. Forster et al.239 pointed out that surface morphology,

surface coatings and grain size of materials can cause attenuation

of incident and fluorescent X-rays, yet appropriate mathematical

corrections can provide a high level of accuracy and precision.

Qualitative analysis with portable systems has been applied for a

more efficient sampling, i.e., soil sampling,222 in order to perform a

fast general screening of the soil composition and detect the points

of contamination. It allows selecting representative points, thereby

saving time in the sampling stage.

WDXRF is mainly applied for direct solid analysis (soils,

metals, ceramics, etc.) in routine labs. WDXRF analysis splits

the characteristic wavelengths with a high resolution, which is

especially relevant for light elements (LODs at the ppm level).180

It is faster than EDXRF and TXRF (i.e., 100 s vs. 500 s). In

contrast to mXRF and EDXRF, portable systems for WDXRF

are not available. So in WDXRF analysis, sampling and trans-

port of the sample to the lab are needed. In general, sample

consumption is higher compared to other X-ray techniques, i.e.,

only a few micrograms of sample are necessary in TXRF and

EDXRF vs. 0.1–5.0 g in WDXRF.221,240–242 The analysis is

usually carried out under vacuum, and for the analysis of loose

powders, an inert atmosphere (He or N2) is needed to prevent air

from absorbing the fluorescence X-rays. As in TXRF and

EDXRF, the use of an automatic sample changer is possible.

5. Greening instrumentation for atomic spectrometry

Nowadays, remarkable greenness in atomic spectrometry has

been reached through miniaturization, automation and design of

cost-effective systems, which allow lower consumption of gases

(e.g., fuel, plasmogen, carrier), samples and reagents, and/or

simplified sample pre-treatment. Improvements made in instru-

mentation for atomic spectrometry (including inorganic mass

spectrometry) from the early prototypes to the modern instru-

ments have also contributed to reach higher levels of greenness.

As an example, implementation of efficient background correc-

tion systems in the early atomic absorption spectrometers made



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


it possible to carry out many applications with a significant

saving in operations such as matrix elimination by typical

procedures, which in turn, brought about a decrease in errors.243

More recently, the development of efficient collision and reaction

cells for elimination of some interferences caused by polyatomic

ions has simplified the application of quadrupolar ICP-MS to

complex matrices.244

Undoubtedly, major developments made in most atomic

spectrometric techniques have run in parallel with improvements

of green features. For instance, automation provided by modern

autosamplers in techniques such as ETAAS, allowing intelligent

dilution, injection of sample, diluents and matrix modifiers at

any sequence, performing calibration curve from one single

standard, recalibration, etc. has dramatically changed method

development with this technique, hence saving time, efforts and

decreasing errors.

A component that is commonly used for sample introduction in

atomic spectrometry is the pneumatic nebulizer. Development of

miniaturized nebulizers that allow minimum consumption of

sample is one of the goals of GAC. In contrast to conventional

nebulizers,micronebulizers allow the generationof a stable aerosol

at liquid flow-rates on the order of several microliters per

minute.245 Additional advantages of micronebulizers are the very

low dead volumes and lesser memory effects. Micronebulizers

originate finer primary aerosols, higher solution transport rates

and higher sensitivity as compared to conventional pneumatic

nebulizers, yet some prototypes are prone to blocking.246 The

suitability of several micronebulizers for analysis of microsamples

has been shown for techniques suchas ICP-OES247andICP-MS.248

The design of efficient sample introduction systems such as

those based on thermospray interfaces has allowed an improve-

ment in LODs apart from decreasing the sample consumption. In

the thermospray technique, the liquid is pumped through a

capillary and heated uniformly along a length of a few cm. The

heating causes the liquid to partially vaporize, giving rise to a

blast of vapour that converts the remaining liquid to droplets.

This interface has been used in conjunction with several tech-

niques such as ICP-OES, ICP-MS, FAAS and ETAAS.249 As a

result of the increased sensitivity achieved with the thermospray

technique, this interface can also benefit the coupling between

HPLC and atomic spectrometry for speciation studies.250

Greening atomizers for atomic spectrometry is another area of

research. Efforts have been made in decreasing the power and gas

consumption as well as the size of atomizers in order to approach

the concept of ‘portable instrument’.

With the arrival of plasma techniques (i.e., ICP-OES, ICP-

MS), multielement analysis at a trace level has been facilitated.

However, the high operating cost represented by the Ar

consumption can limit their application in smaller labs. Thus,

conventional ICP torches have been modified so that the Ar and

power consumption can be reduced. One way to reduce Ar

consumption is the design of minitorches.251 Nevertheless, those

systems are somewhat more prone to interferences in comparison

with conventional torches.

Microplasmas for atomic emission have been described, e.g.,

high-frequency plasmas, dc-discharges, MW plasmas.252

However, the heat capacity of these systems is limited and sample

introduction in the vapour phase instead of liquid phase is

mandatory. In this way, typical derivatization techniques such as


hydride generation are useful. These approaches are not free from

drawbacks due to the unstabilizing effect caused by the excess

hydrogen generated during chemical hydride generation. Alter-

native HG procedures such as those based on electrochemical

hydride generation or UV reduction are promising.253,254 Other

strategies for spreading the applicability ofmicroplasmas are their

use as detectors in gas chromatography255 or the generation of dry

vapours using electrothermal vaporization.256

Miniaturized flames have been also developed for atomization

of volatile compounds.Thus,miniaturized diffusionflames suchas

Ar/H2 have found application for AFS after HG.257These systems

offer low consumption of gases, low background emission and

lesser interferences as compared with other atomizers.258 Multi-

atomizers configured inside a quartz tube allow achieving

improved sensitivity as comparedwith diffusion flames apart from

enhanced linearity and resistance against interferences in

comparison with quartz tubes.259 The multiatomizer is similar to

conventional quartz tube atomizers, but it is punctured over the

horizontal arm so that air can be dosed through the orifices to the

optical inner volume. In thisway,multiplemicroflames arise inside

the tube as a result of themultiple hydrogen radical clouds formed.

Efficient atomic fluorescence detectors have been marketed

using the hydrogen generated in the reaction with sodium tet-

rahydroborate to feed a miniaturized diffusion flame of Ar/H2

with application in total trace analysis (Hg, As, Se, Te, Sb, Bi)

and as specific detectors for speciation when interfaced with

liquid or gas chromatography.260

Miniaturization has also spread to hyphenated techniques for

speciation in biological systems. Thus, for metallome analysis in

small amounts of tissues and cells, new tools based on minia-

turized HPLC techniques (e.g., narrow bore, capillary and nano-

HPLC) coupled to ICP-MS have been developed, which are

expected to clarify the physiological and biological roles of

metalloproteins.261 The coupling between capillary and, espe-

cially, nano-flow HPLC with ICP-MS demands for the devel-

opment of suitable interfaces so that the sample uptake is

compatible with the mobile phase flow-rate. For this, micro-

nebulizers discussed above are required.262

Other green couplings between HPLC and ICP-MS for

speciation of hydride forming elements are based on on-line UV/

TiO2 photocatalysis, thus eliminating conventional hydride

generation with the NaBH4–NaOH system.263

An interesting technique avoiding time-consuming procedures

for preconcentration is the use of ‘in-atomizer’ trapping. This

approach has been tried in different ways.

First systems were based on trapping in a graphite tube for

electrothermal atomization.264 Apart from improving sensitivity,

in situ trapping eliminates the effect of kinetic interferences inHG.

Moreover, these systems can be easily automated. More recently,

trapping onto quartz surfaces in an excess oxygen and further

atomization in multiatomizers or conventional quartz tubes have

also been proposed to achieve very low detection limits.258 Trap-

ping of volatile hydrides has also been performed in miniature

electrothermal devices, e.g., tungsten coil265 and bare and modi-

fied strips with noble metals (Pt, Ir, Rh).266 W-coil devices can be

used as atomizers for ETAAS, electrothermal atomizer laser-

excited atomic fluorescence spectrometry (ETA-LEAFS) and

ETV-ICP-OES, being ideal for the design of low-cost, compact

and portable instrumentation for field environmental and clinical



Fig. 6 Examples of miniaturized and low consumption atomizers for atomic absorption spectrometry (Ref. 250, 255, 265, 267 and 268).

Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


analysis.267 W-coil atomizers along with a simple CCD-based

spectrometer make the development of AAS instrumentation for

field analysis possible. A few representative examples of minia-

turized atomizers for AAS are shown in Fig. 6.

The recent implementation of fast multielemental sequential

analysis in AAS through novel instrumentation based on

continuous radiation sources (Xe-arc lamp), echelle mono-

chromators and CCD detectors can be considered a step forward

in the achievement of greener AAS methods.269 The observation

of the analytical line at high resolution facilitates method

development and helps avoiding spectral interferences.

As indicated above, most successful achievements so far

toward the achievement of portable instruments have been

reported in the miniaturization of techniques such as XRF and

LIBS. These techniques are essentially non-destructive, fast and

they provide instantaneous multi-element analysis.2

6. Chemometrics for greening atomic spectrometrymethods

Can chemometrics be a tool for greening atomic spectrometry

methods? According to Namie�snik,270 the reduction of labour-

intensive procedures, energy and reagent consumption is essential

for the implementation of GAC principles. Automation and

robotization, multianalyte determination in a single analytical

cycle and wider utilization of hyphenated techniques are consid-

ered by this author as the main ways for greening the analytical

laboratory. There is no doubt that chemometrics is of paramount

importance to achieve the aforementioned developments, hence

being an indirect way of saving time, labour, energy and reagents.

In general, chemometrics helps extracting information with a

smaller number of experiments and preventing errors in an


environmentally friendlyway. In spite of this, chemometrics is not

usually considered from the point of view of GAC.

In this regard, Armenta et al.4 as well as Koel and Kaljurand2

recognize the importance of chemometrics in the development of

solvent free methodologies based on direct measurements

without sample pre-treatment. Particularly, this conception has

been focused on molecular spectroscopy techniques that involve

large amounts of spectral data, such as UV-vis spectrometry,

fluorescence, near infrared (NIR), mid-infrared (MIR) and

nuclear magnetic resonance (NMR). Some examples taken into

consideration by these authors are the use of calibration by

partial least squares (PLS) in NIR,MIR or Raman spectroscopy,

thereby enhancing the application of these techniques in the

analytical lab on a routine basis4 or the use of parallel factor

analysis (PARAFAC) in the resolution of mixtures using exci-

tation–emission spectroscopy (EEM).2

Chemometrics (including exploring data, optimization, cali-

bration, signal processing, pattern recognition and artificial

intelligence) can be considered also as an interesting tool for

greening atomic spectrometry methods. As mentioned above,

chemometrics become particularly significant to reduce the

number of measurements or to obtain much simpler and efficient

analytical procedures with atomic spectrometry techniques.

To a greater or lesser extent, chemometrics is involved in all

steps of analytical methods, from development and validation up

to data evaluation. For instance, principal component analysis

(PCA) and a multi-criteria target function have been used in ICP-

MS for 83 isotopes and 21 operating parameters.271 Chemo-

metrics has been also used to evaluate the combined uncertainty

for mercury speciation by GC-AFS in the validation step.272

Multivariate techniques for pattern recognition are being

increasingly applied to trace metals data in order to discriminate



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


between samples. In general, well-established chemometric tools

are used, e.g., PCA, cluster analysis (CA), linear discriminant

analysis (LDA), soft independent modelling of class analogy

(SIMCA) or artificial neural networks (ANNs). Practically, we

can find applications in all fields of interest such as clinical273 and

environmental,274 but in particular in food science for estab-

lishing geographical origins, e.g., honeys,275 onions,276 alcoholic

beverages,277 coffee,278 mussels,279 etc.

Though optimization is fundamental in the development of

analytical methods, the most usual approach for this purpose in

atomic spectrometry continues to be the non-systematic way,

based on the subjective experience of the analytical chemist (trial-

and-error approach). If this experience is less, the workload in

the laboratory is large and, in addition, optimization is not

guaranteed.280 In most cases, optimization is carried out using a

univariate strategy. It implies a large number of experiments,

which increase the consumption of reagents and are labour-

intensive. In order to overcome these disadvantages, multivariate

optimization is a more desirable option from the point of view of

GAC. Different strategies have been used in atomic spectrom-

etry, in particular experimental design and response surface

methods.281 In those methods, different variables are simulta-

neously and systematically studied. In addition, they provide

more information about variables (e.g., interaction between

them) with fewer experiments, which is especially important for

optimizing sample preparation stages, e.g. microwave-assisted

digestion,282 preconcentration using different sorbents,283,284 etc.

Optimization of measurement conditions in different atomic

spectrometric techniques is also carried out with multivariate

strategies, e.g., application of the experimental design for opti-

mization of lead determination by high-resolution continuum

source hydride generation atomic absorption spectrometry.285

Experimental design for method optimization using spectro-

metric techniques has been reviewed by Bianchi and Careri.286

Hibbert and Armstrong287 have reviewed the applications of

Bayesian methods, including spectroscopy and mass spectrom-

etry. The use of response surface methodology for optimization

in analytical chemistry has been reviewed by Bezerra et al.288

Multivariate calibration methods represent a useful strategy to

fight analyte interferences, so these can be considered as impor-

tant tools from the standpoint of GAC. A tutorial review on

multivariate calibration in atomic spectrometry techniques has

been published by Andrade et al.289 These authors include among

the advantages of multivariate calibration ‘lower workloads,

increased laboratory turnarounds, economy, higher efficiency in

method development, and relatively simple ways to take account

of complex interferences’, all of which are directly related to

GAC. Application of multiple ordinary least squares regression

(MOLSR), principal components regression (PCR), PLS and

ANN on FAAS, HG-AAS, ETAAS, ICP-OES and LIBS are

presented in a practice-oriented way. These multivariate cali-

bration methods may be applied to monoelemental techniques

considering the transient signals (absorbance vs. time) as a

spectrum (absorbance at multiple wavelengths).

On the other hand, signal processing can be considered as a

simple way for improving instrumental performances without

hardware component changes and/or replacement by expensive

systems.290 Signal processing is used to enhance signal vs. noise,

to improve peak resolution, to decompose complex signals, etc.


Undoubtedly, it allows extracting more information from

analytical data with a lower number of experiments. For

example, chemical interference correction, including separation,

can be replaced or minimized by chemometric interference

correction. Mathematical algorithms for background modelling

and correction have been designed and applied to different

atomic techniques in order to improve their analytical charac-

teristics.291–296 At present, signal processing is an active field

especially when transient signals are obtained. For instance,

Chaves et al.297 proposed the processing of fast transient signals

provided by different sample introduction systems (FI, LA, GC,

HPLC) with modern simultaneous ICP-OES instruments. Pri-

kler et al.298 compared different strategies as convolution with

Gaussian distribution curves, Fourier transform, and wavelet

transform for improving the detection power in HPLC-ICP-MS.

A total signal integration method has been proposed as an

alternative to quantify transient signals with LA and ICP-MS.299

In general, application of artificial intelligence (AI), especially

expert systems (ES), intelligent analysers and robot systems,

constitutes an efficient way so as to turn the analytical lab green,

since lab efficiency is increased and the occupational exposure of

the personnel and reagent consumption are decreased.280,300 An

intelligentized analytical lab results in a more cost-effective use of

staff and resources. AI can be used from the selection and opti-

mization of an analytical method up to the final report, including

detection of malfunctions and validation. During the 90s, a large

number of ESs were developed for different atomic spectrometry

applications. ESs are programs with a heuristic knowledge based

on the experience of experts. ESs have been included in FAAS

spectrometers for full automation (in particular for error detec-

tion and correction).301 In ICP-OES, ESs are used for prediction

and correction of spectral interferences,302,303 spectral line simu-

lation and selection,304,305 system diagnosis306 or as a hybrid

expert-database system for sample preparation by microwave-

assisted dissolution.307,308 ES has been also used in ICP-MS for

controlling the spectrometer,309,310 the whole sample pre-treat-

ment process311 and developing a simple diagnostic procedure to

automatically ensure the quality of results.312 In XRF, it has been

applied for the evaluation of different possibilities in the reso-

lution of a given analytical problem.313,314 Intelligent analysers

have also been designed with different atomic spectometers,315–317

i.e., an intelligent flow system has been proposed for the on-line

speciation of metal ions at a wide range of concentrations

without requiring manifold reconfiguration.316

7. Conclusions

A remarkable greenness can be achieved when GAC principles

are applied to Atomic Spectrometry. For this, every stage of the

analytical process should be focused. Advances in instrumenta-

tion, sample preparation techniques, chemometric treatment of

data, etc. can drive significant improvements not only in

analytical characteristics but also in green issues of the whole

methodology. Labs involved in trace metal analysis can benefit

from the concepts of green chemistry, since apart from advan-

tages inherent to the implementation of automated, simplified,

accelerated and miniaturized systems, there is also a great

conservation of reagents, solvents and energy, less risks to the

analyst, and less production of wastes. More progress is expected



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


over the next years concerning this topic with the downsizing of

instruments, implementation of new materials (e.g., nano-

materials) and development of analytical devices for on-site

determination.

List of abbreviations

AAS

1852 | J. Anal. At.

Atomic absorption spectrometry

AFS
Atomic fluorescence spectrometry
AI
Artificial intelligence
ANNs
Artificial neural networks
AOPs
Advanced oxidation processes
ASE
Accelerated solvent extraction
BI
Bead-injection
CA
Cluster analysis
CCD
Charge-coupled devices
CPE
Cloud point extraction
CV
Cold vapour
CVG
Chemical vapour generation
DBD
Dielectric barrier discharge
dc
Direct current
DSI
Direct solid insertion
EC-HG
Electrochemical hydride generation
EDXRF
Energy dispersive X-ray fluorescence
EEM
Excitation-emission spectroscopy
ES
Expert systems
ETAAS
Electrothermal atomic absorption
spectrometry

ETA-LEAFS
Electrothermal atomizer laser-excited atomic
fluorescence spectrometry

ETV
Electrothermal vaporization
FAAS
Flame atomic absorption spectrometry
FI
Flow injection
FIA
Flow injection analysis
FMAE
Focused microwave-assisted extraction
GAC
Green analytical chemistry
GC
Gas chromatography
GD
Glow discharge
GSK
GlaxoSmithKline
HEPO
High-efficiency photooxidation
HF
Hollow fiber
HG
Hydride generation
HIFU
High-intensity focused ultrasound
HPLC
High performance liquid chromatography
HS
Headspace
ICP-MS
Inductively coupled plasma-mass
spectrometry

ICP-OES
Inductively coupled plasma-optical emission
spectrometry

IL
Ionic liquid
LA
Laser ablation
LAM
Laser ablation microprobe
LC
Liquid chromatography
LDA
Linear discriminant analysis
LIBS
Laser induced breakdown spectroscopy
LLE
Liquid–liquid extraction
LOC
Lab-on-a-chip
LODs
Limits of detection
Spectrom., 2012, 27, 1831–1857

LOV

This

Lab-on-valve

LPME
Liquid-phase microextraction
MAD
Microwave-assisted digestion
MAE
Microwave-assisted extraction
MCFIA
Multicommutated flow injection analysis
m-FIA
Micro-flow injection analysis
m-TAS
Micro-total analytical system
m-XRF
Micro-X-ray fluorescence
MIR
Mid-infrared
MOLSR
Multiple ordinary least squares regression
MPFS
Multipumping flow system
MS
Mass spectrometry
MSFIA
Multisyringe flow injection analysis
MSPME
Magnetic nanoparticle solid phase
microextraction

MW
Microwave
Nd:YAG
Neodymium:yttrium aluminium garnet
NEMI
National environment methods index
NIR
Near infrared
NmimCl
1-Chlorovinyl-3-methylimidazolium chloride
NMR
Nuclear magnetic resonance
OES
Optical emission spectrometry
PARAFAC
Parallel factor analysis
PCA
Principal component analysis
PCR
Principal components regression
PLE
Pressurized liquid extraction
PLS
Partial least squares
PMAE
Pressurized microwave-assisted extraction
PMI
Positive material identification
PTFE
Polytetrafluoroethylene
PVC
Polyvinyl chloride
QFAAS
Quartz furnace atomic absorption
spectrometry

REM
Roentgen Equivalent Man
rf
Radio frequency
SBSE
Stir bar sorptive extraction
SDS
Sodium dodecyl sulphate
SEM
Scanning electron microscopy
SFE
Supercritical fluid extraction
SIA
Sequential injection analysis
SIMCA
Soft independent modelling of class analogy
SIMS
Secondary ion mass spectrometry
SLM
Supported liquid membrane
SN
Slurry nebulization
SPE
Solid-phase extraction
SPME
Solid-phase microextraction
SS
Slurry sampling
SSEA
Separate sampling and excitation accessory
ToF
Time-of-flight
TRS
Time-resolved spectroscopy
TXRF
Total reflection X-ray fluorescence
UAE
Ultrasound-assisted extraction
US
Ultrasound
USAED
Ultrasound-assisted enzymatic digestion
USS
Ultrasonic slurry sampling
VUV
Vacuum ultraviolet
WDXRF
Wavelength dispersive X-ray fluorescence
XRF
X-ray fluorescence
journal is ª The Royal Society of Chemistry 2012


Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


Acknowledgements

Financial support from the Spanish Ministry of Economy and

Competitiveness (Project CTQ2009-06956/BQU), the Xunta de

Galicia (project 10PXIB 314030 PR) and the Vigo University

(Contract for Reference Research Groups 09VIA08) is gratefully

acknowledged. The Spanish Ministry of Education, Culture and

Sport is acknowledged for financial support through a FPU pre-

doctoral grant to Vanesa Romero. The Portuguese Foundation

for Science andTechnology is acknowledged for financial support

through a Post-Doctoral grant to Francisco Pena-Pereira.

References

1 P. T. Anastas and J. C. Warner, Green Chemistry: Theory andPractice, Oxford University Press, New York, 1998.

2 M. Koel and M. Kaljurand, Green Analytical Chemistry, RoyalSociety of Chemistry, Cambridge, 2010.

3 M. de la Guardia and S. Garriges, Challenges in Green AnalyticalChemistry, Royal Society of Chemistry, Cambridge, 2011.

4 S. Armenta, S. Garrigues and M. de la Guardia, TrAC, Trends Anal.Chem., 2008, 27, 497–511.

5 M. Tobiszewski, A. Mechli�nska, B. Zygmunt and J. Namie�snik,TrAC, Trends Anal. Chem., 2009, 28, 943–951.

6 M. Tobiszewski, A. Mechlinska and J. Namie�snik, Chem. Soc. Rev.,2010, 39, 2869–2878.

7 M. de la Guardia, TrAC, Trends Anal. Chem., 2010, 29, 577.8 C. J. Welch, M. Biba, R. Hartman, T. Brkovic, X. Gong, R. Helmy,W. Schafer, J. Cuff, Z. Pirzada and L. Zhou, TrAC, Trends Anal.Chem., 2010, 29, 667–680.

9 F. Pena-Pereira, I. Lavilla and C. Bendicho, TrAC, Trends Anal.Chem., 2010, 29, 617–628.

10 S. Garrigues, S. Armenta and M. de la Guardia, TrAC, Trends Anal.Chem., 2010, 29, 592–601.

11 C. Bendicho, F. Pena, M. Costas, S. Gil and I. Lavilla, TrAC, TrendsAnal. Chem., 2010, 29, 681–691.

12 A. Molina-Diaz, J. F. Garc�ıa-Reyes and B. Gilbert-L�opez, TrAC,Trends Anal. Chem., 2010, 29, 654–666.

13 M. Farr�e, S. P�erez, C. Goncalves, M. F. Alpendurada andD. Barcel�o, TrAC, Trends Anal. Chem., 2010, 29, 1347–1362.

14 M. Tobiszewski and J. Namie�snik, TrAC, Trends Anal. Chem., 2012,25, 67–73.

15 C. Bendicho, I. de La Calle, F. Pena, N. Cabaleiro and I. Lavilla,TrAC, Trends Anal. Chem., 2012, 31, 50–60.

16 http://www.nemi.gov, last accessed, June 2012.17 A. Galuszka, P. Konieczka, Z. M. Migaszewski and J. Namie�snik,

TrAC, Trends Anal. Chem., 2012, 37, 61–72.18 V. Camel, Spectrochim. Acta, Part B, 2003, 58, 1177–1233.19 C. Bendicho, I. Lavilla, F. Pena and M. Costas, in Challenges in

Green Analytical Chemistry, ed. M. de la Guardia and S.Garrigues, Royal Society of chemistry, Cambridge, 2011, pp. 63–99.

20 V. A. Lemos, L. S. G. Teixeira, M. A. Bezerra, A. C. S. Costa,J. T. Castro, L. A. M. Cardoso, D. S. de Jesus, E. S. Santos,P. X. Baliza and L. N. Santos, Appl. Spectrosc. Rev., 2008, 43,303–334.

21 M. L. Chen, Y. N. Zhao, D. W. Zhang, Y. Tian and J. H. Wang, J.Anal. At. Spectrom., 2010, 25, 1688–1694.

22 Y. Tian, Z. M. Xie, M. L. Chen and J. H. Wang, J. Anal. At.Spectrom., 2011, 26, 1408–1413.

23 Z. Mester, R. Sturgeon and J. Pawliszyn, Spectrochim. Acta, Part B,2001, 56, 233–260.

24 Z. Mester and R. Sturgeon, Spectrochim. Acta, Part B, 2005, 60,1243–1269.

25 S. Risticevic, V. H. Niri, D. Vuckovic and J. Pawliszyn, Anal.Bioanal. Chem., 2009, 393, 781–785.

26 F. Pena-Pereira, I. Lavilla and C. Bendicho, Spectrochim. Acta, PartB, 2009, 64, 1–15.

27 S. Dadfarnia and A. M. Haji Shabani, Anal. Chim. Acta, 2010, 658,107–119.

28 F. Pena-Pereira, I. Lavilla and C. Bendicho, Anal. Chim. Acta, 2010,669, 1–16.


29 E. Baltussen, P. Sandra, F. David and C. Cramers, J. MicrocolumnSep., 1999, 11, 737–747.

30 F. David and P. Sandra, J. Chromatogr., A, 2007, 1152, 54–69.31 A. Prieto, O. Basauri, R. Rodil, A. Usobiaga, L. A. Fern�andez,

N. Etxebarr�ıa and O. Zuloaga, J. Chromatogr., A, 2010, 1217,2642–2666.

32 J. Vercauteren, C. P�er�es, C. Devos, P. Sandra, F. Vanhaecke andL. Moens, Anal. Chem., 2001, 73, 1509–1514.

33 J. Millos, M. Costas-Rodr�ıguez, I. Lavilla and C. Bendicho, Anal.Chim. Acta, 2008, 622, 77–84.

34 J. Pacheco-Arjona, P. Rodriguez-Gonzalez, M. Valiente, D. Barclayand O. F. X. Donard, Int. J. Environ. Anal. Chem., 2008, 88, 923–932.

35 I. de la Calle, N. Cabaleiro, I. Lavilla and C. Bendicho, Spectrochim.Acta, Part B, 2009, 64, 874–883.

36 J. L. G�omez-Ariza, V. Bernal-Daza and M. J. Villegas-Portero,Anal. Chim. Acta, 2004, 520, 229–235.

37 A. Moreda-Pi~neiro, J. Moreda-Pi~neiro, P. Herbello-Hermelo,P. Bermejo-Barrera, S. Muniategui-Lorenzo, P. L�opez-Mah�ıa andD. Prada-Rodr�ıguez, J. Chromatogr., A, 2011, 1218, 6970–6980.

38 M. Costas, I. Lavilla, S. Gil, F. Pena, I. de la Calle, N. Cabaleiro andC. Bendicho, Anal. Chim. Acta, 2010, 679, 49–55.

39 M. Zougagh, M. Valc�arcel and A. R�ıos, TrAC, Trends Anal. Chem.,2004, 23, 399–405.

40 M. D. Luque de Castro and M. T. Tena, TrAC, Trends Anal. Chem.,1996, 15, 32–37.

41 J. Kronholm, K. Hartonen andM. L. Riekkola, TrAC, Trends Anal.Chem., 2007, 26, 396–412.

42 V. Camel, Analyst, 2001, 126, 1182–1193.43 L. H. Keith, L. U. Gron and J. L. Young, Chem. Rev., 2007, 107,

2695–2708.44 L. Chimuka and R. Majors, LC$GC Eur., 2004, 17, 396–401.45 J. A. L�opez-L�opez, C. Mendiguch�ıa, J. J. Pinto and C. Moreno,

TrAC, Trends Anal. Chem., 2010, 29, 645–653.46 K. Chakrabarty, P. Saha and A. K. Ghoshal, J. Membr. Sci., 2010,

350, 395–401.47 J. F. Peng, R. Liu, J. F. Liu, B. He, X. L. Hu and G. B. Jiang,

Spectrochim. Acta, Part B, 2007, 62, 499–503.48 L. Xia, Y. Wu and B. Hu, J. Mass Spectrom., 2007, 42, 803–810.49 C. Bosch Ojeda and F. S�anchez Rojas, Anal. Bioanal. Chem., 2009,

394, 759–782.50 C. Ortega, M. R. Gomez, R. A. Olsina, M. F. Silva and

L. D. Martinez, J. Anal. At. Spectrom., 2002, 17, 530–533.51 Y. Yamini, M. Faraji, S. Shariati, R. Hassani and M. Ghambarian,

Anal. Chim. Acta, 2008, 612, 144–151.52 K. Simitchiev, V. Stefanova, V. Kmetov, G. Andreev, N. Kovachev

and A. Canals, J. Anal. At. Spectrom., 2008, 23, 717–726.53 N. N. Meeravali and S. J. Jiang, J. Anal. At. Spectrom., 2008, 23,

1365–1371.54 M. Faraji, Y. Yamini and M. Rezaee, Talanta, 2010, 81, 831–836.55 A. E. Karatapanis, Y. Fiamegos and C. D. Stalikas, Talanta, 2011,

84, 834–839.56 R. Q. Auc�elio, R. M. de Souza, R. C. de Campos, N. Miekeley and

C. L. P. da Silveira, Spectrochim. Acta, Part B, 2007, 62, 952–961.57 I. Lavilla, N. Cabaleiro, M. Costas, I. de la Calle and C. Bendicho,

Talanta, 2009, 80, 109–116.58 P. R. Aranda, P. H. Pacheco, R. A. Olsina, L. D. Martinez and

R. A. Gil, J. Anal. At. Spectrom., 2009, 24, 1441–1445.59 R. J. Cassella, D. M. Brum, C. E. R. de Paula and C. F. Lima, J.

Anal. At. Spectrom., 2010, 25, 1704–1711.60 P. Tundo, P. Anastas, D. StC. Black, J. Breen, T. Collins, S. Memoli,

J. Miyamoto, M. Polyakoff and W. Tumas, Pure Appl. Chem., 2000,72, 1207–1228.

61 E. M. Martinis, P. Berton, R. P. Monasterio and R. G. Wuilloud,TrAC, Trends Anal. Chem., 2010, 29, 1184–1201.

62 S. Jafarvand and F. Shemirani, Microchim. Acta, 2011, 173, 353–359.

63 C. Erkey, J. Supercrit. Fluids, 2000, 17, 259–287.64 L. Xia, B. Hu, Z. Jiang, Y. Wu and Y. Liang, Anal. Chem., 2004, 76,

2910–2915.65 X. Jia, Y. Han, X. Liu, T. Duan and H. Chen, Spectrochim. Acta,

Part B, 2011, 66, 88–92.66 P. T. Anastas, in Clean Solvents: Alternative Media for Chemical

Reactions and Processing, ed. M.A. Abraham and L. Moens,American Chemical Society, Washington, DC, 2002, pp. 1–9.



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


67 P. G. Jessop, Green Chem., 2011, 13, 1391–1398.68 R. K. Henderson, C. Jim�enez-Gonz�alez, D. J. C. Constable,

S. R. Alston, G. G. A. Inglis, G. Fisher, J. Sherwood, S. P. Binksand A. D. Curzons, Green Chem., 2011, 13, 854–862.

69 K. Alfonsi, J. Colberg, P. J. Dunn, T. Fevig, S. Jennings,T. A. Johnson, H. P. Kleine, C. Knight, M. A. Nagy, D. A. Perryand M. Stefaniak, Green Chem., 2008, 10, 31–36.

70 http://www.rsc.org/suppdata/gc/c0/c0gc00918k/c0gc00918k.pdf, lastaccessed June 2012.

71 P. Cava-Montesinos, E. R�odenas-Torralba, A. Morales-Rubio,M. L. Cervera and M. de la Guardia, Anal. Chim. Acta, 2004, 506,145–153.

72 E. R�odenas-Torralba, P. Cava-Montesinos, A. Morales-Rubio,M. L. Cervera and M. de la Guardia, Anal. Bioanal. Chem., 2004,379, 83–89.

73 R. B. R. Mesquita and A. O. S. S. Rangel, Anal. Chim. Acta, 2009,648, 7–22.

74 Y. L. Yu, Z. Du, M. L. Chen and J. H. Wang, J. Anal. At. Spectrom.,2007, 22, 800–806.

75 Y. L. Yu, Y. Jiang, M. L. Chen and J. H. Wang, TrAC, Trends Anal.Chem., 2011, 30, 1649–1658.

76 L. Xia, X. Li, Y. Wu, B. Hu and R. Chen, Spectrochim. Acta, Part B,2008, 63, 1290–1296.

77 Y. Li, C. Zheng, Q. Ma, L. Wu, C. Hu and X. Hou, J. Anal. At.Spectrom., 2006, 21, 82–85.

78 S. Z. Mohammadi, D. Afzali and Y. M. Baghelani, Anal. Chim.Acta, 2009, 653, 173–177.

79 H. Sereshti, V. Khojeh, M. Karimi and S. Samadi, Anal. Methods,2012, 4, 236–241.

80 S. Z. Mohammadi, D. Afzali, M. A. Taher and Y. M. Baghelani,Talanta, 2009, 80, 875–879.

81 K. Grudpan, S. K. Hartwell, S. Lapanantnoppakhuna andI. McKelvie, Anal. Methods, 2010, 2, 1651–1661.

82 M. Tuzen, O. D. Uluozlu and M. Soylak, J. Hazard. Mater., 2007,144, 549–555.

83 M. Tuzen, O. D. Uluozlu, I. Karaman and M. Soylak, J. Hazard.Mater., 2009, 169, 345–350.

84 C. Zhang, Y. Li, X. Y. Cui, Y. Jiang and X. P. Yan, J. Anal. At.Spectrom., 2008, 23, 1372–1377.

85 C. Zeng, N. Zhou and J. Luo, J. Anal. At. Spectrom., 2012, 27, 120–125.86 P. Wu, L. He, C. Zheng, X. Hou and R. E. Sturgeon, J. Anal. At.

Spectrom., 2010, 25, 1217–1246.87 X. Guo, R. E. Sturgeon, Z. Mester and G. J. Gardner, Anal. Chem.,

2003, 75, 2092–2099.88 C. Zheng, Y. Li, Y. He, Q. Ma and X. Hou, J. Anal. At. Spectrom.,

2005, 20, 746–750.89 Y. He, X. Hou, C. Zheng and R. E. Sturgeon, Anal. Bioanal. Chem.,

2007, 388, 769–774.90 M. A. Vieira, A. S. Ribeiro, A. J. Curtius and R. E. Sturgeon, Anal.

Bioanal. Chem., 2007, 388, 837–847.91 C. Zheng, R. E. Sturgeon and X. Hou, J. Anal. At. Spectrom., 2009,

24, 1452–1458.92 C. Han, C. Zheng, J. Wang, G. Cheng, Y. Lv and X. Hou, Anal.

Bioanal. Chem., 2007, 388, 825–830.93 S. Gil, I. Lavilla and C. Bendicho, Anal. Chem., 2006, 78, 6260–6264.94 S. Gil, I. Lavilla and C. Bendicho, Spectrochim. Acta, Part B, 2007,

62, 69–75.95 A. S. Ribeiro, M. A. Vieira, S. Willie and R. E. Sturgeon, Anal.

Bioanal. Chem., 2007, 388, 849–857.96 S. Gil, I. Lavilla and C. Bendicho, J. Anal. At. Spectrom., 2007, 22,

569–572.97 F. Laborda, E. Bolea and J. R. Castillo, Anal. Bioanal. Chem., 2007,

388, 743–751.98 X. Wu, W. Yang, M. Liu, X. Hou and C. Zheng, J. Anal. At.

Spectrom., 2011, 26, 1204–1209.99 Q. Wu, Z. Zhu, Z. Liu, H. Zheng, S. Hu and L. Li, J. Anal. At.

Spectrom., 2012, 27, 496–500.100 J. L. Capelo-Mart�ınez, P. Xim�enez-Emb�un, Y. Madrid and

C. C�amara, TrAC, Trends Anal. Chem., 2004, 23, 331–340.101 F. Fern�andez-Costas, I. Lavilla and C. Bendicho, Spectrosc. Lett.,

2006, 39, 713–725.102 J. L. Capelo, I. Lavilla and C. Bendicho, Anal. Chem., 2000, 72,

4979–4984.103 J. L. Capelo, I. Lavilla and C. Bendicho, Anal. Chem., 2001, 73,

3732–3736.


104 J. L. Capelo, C. Maduro and A. M. Mota, J. Anal. At. Spectrom.,2004, 19, 414–416.

105 T. Nakazato and H. Tao, Anal. Chem., 2006, 78, 1665–1672.106 L. Abrank�o, L. Yang, R. E. Sturgeon, P. Fodor and Z. Mester, J.

Anal. At. Spectrom., 2004, 19, 1098–1103.107 R. Pe~nalver, N. Campillo and M. Hern�andez-C�ordoba, Talanta,

2011, 87, 268–275.108 M. S. Fragueiro, F. Alava-Moreno, I. Lavilla and C. Bendicho, J.

Anal. At. Spectrom., 2000, 15, 705–709.109 S. Fragueiro, I. Lavilla and C. Bendicho, J. Anal. At. Spectrom.,

2004, 19, 250–254.110 C. Dietz, T. P�erez-Corona, Y. Madrid-Albarr�an and C. C�amara, J.

Anal. At. Spectrom., 2003, 18, 467–473.111 P. Hashemi and A. Rahimi, Spectrochim. Acta, Part B, 2007, 62,

423–428.112 A. Zierhut, K. Leopold, L. Harwardt, P. Worsfold and M. Schuster,

J. Anal. At. Spectrom., 2009, 24, 767–774.113 V. Romero, I. Costas-Mora, I. Lavilla and C. Bendicho,

Spectrochim. Acta, Part B, 2011, 66, 156–162.114 C. Pons, R. Forteza, A. O. S. S. Rangel and V. Cerd�a, TrAC, Trends

Anal. Chem., 2006, 25, 583–588.115 A. Economou, TrAC, Trends Anal. Chem., 2005, 24, 416–425.116 W. C. Tseng, P. H. Chen, T. S. Tsay, B. H. Chen and Y. L. Huang,

Anal. Chim. Acta, 2006, 576, 2–8.117 J. Ruzicka and E. H. Hansen, Anal. Chim. Acta, 1975, 78, 145–157.118 M. Tokeshi and T. Kitamori, in Advances in Flow Analysis, ed. M.

Trojanowicz, Wiley VCH, Weinheim, 2008, pp. 149–165.119 R. Pereiro, in Flow Analysis with Atomic Spectrometric Detectors, ed.

A. Sanz-Medel, Elsevier, Amsterdam, 1999, pp. 34–61.120 L. J. Shao, W. E. Gan, W. B. Zhang and Q. D Su, J. Anal. At.

Spectrom., 2005, 20, 1296–1298.121 G. Vermeir, C. Vandecasteele and R. Dams, Anal. Chim. Acta, 1991,

242, 203–208.122 S. Armenta and M. de la Guardia, in Challenges in Green Analytical

Chemistry, ed. M. de la Guardia and S. Garrigues, Royal Society ofChemistry, Cambridge 2011, pp. 286–298.

123 T. Taniai, A. Sakuragawa and A. Uzawa, ISIJ Int., 2004, 44, 1852–1858.

124 G. Tao and Z. Fang, Spectrochim. Acta, Part B, 1995, 50, 1747–1755.125 R. M. Cresp�on-Romero and M. C. Yebra-Biurrun, Anal. Chim.

Acta, 2008, 609, 184–191.126 C. Cui, M. He and B. Hu, J. Hazard. Mater., 2011, 187, 379–385.127 A. Maquieira, H. A. M. Elmahadi and R. Puchades, Anal. Chem.,

1994, 66, 3632–3638.128 P. Giusti, Y. N. Ordo~nez, C. P. Lienemann, D. Schauml€offel,

B. Bouyssiere and R. qobi�nski, J. Anal. At. Spectrom., 2007, 22,88–92.

129 N. Homazava, A. Ulrich and U. Kr€ahenb€uhl, Spectrochim. Acta,Part B, 2008, 63, 777–783.

130 N. Homazava, T. Suter, P. Schmutz, S. Toggweiler, A. Grimberg,U. Kr€ahenb€uhl and A. Ulrich, J. Anal. At. Spectrom., 2009, 24,1161–1169.

131 Y. Takasaki, M. Watanabe, H. Yukawa, A. Sabarudin, K. Inagaki,N. Kaji, Y. Okamoto, M. Tokeshi, Y. Miyamoto, H. Noguchi,T. Umemura, S. Hayashi, Y. Baba and H. Haraguchi, Anal.Chem., 2011, 83, 8552–8558.

132 J. Ruzicka, G. D. Marshall and G. D. Christian, Anal. Chem., 1990,62, 1861–1866.

133 M. Mir�o, V. Cerd�a and J. M. Estela, TrAC, Trends Anal. Chem.,2002, 21, 199–210.

134 W. E. Doering, R. R. James and R. T. Echols, Fresenius’ J. Anal.Chem., 2000, 368, 475–479.

135 G. Tao, S. N. Willie and R. E. Sturgeon, Analyst, 1998, 123, 1215–1218.

136 R. C. D. Costa and A. N. Ara�ujo, Anal. Chim. Acta, 2001, 438, 227–233.

137 A. N. Anthemidis, Talanta, 2008, 77, 541–545.138 A. N. Anthemidis and K. I. G. Ioannou, Anal. Chim. Acta, 2010,

668, 35–40.139 J. Wang and E. H. Hansen, J. Anal. At. Spectrom., 2002, 17, 248–

252.140 B. F. Reis, M. F. Gin�e, E. A. G. Zagatto, J. L. F. C. Lima and

R. A. S. Lapa, Anal. Chim. Acta, 1994, 293, 129–138.141 V. Cerd�a, R. Forteza and J. M. Estela, Anal. Chim. Acta, 2007, 600,

35–45.



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


142 M. Pist�on andM. Knochen, Int. J. Anal. Chem., 2012, DOI: 10.1155/2012/918292.

143 L. O. Leal, N. V. Semenova, R. Forteza and V. Cerd�a, Talanta, 2004,64, 1335–1342.

144 Y. Fajardo, E. G�omez, F. Garcias, V. Cerd�a and M. Casas, Anal.Chim. Acta, 2005, 539, 189–194.

145 R. A. S. Lapa, J. L. F. C. Lima, B. F. Reis, J. L. M. Santos andE. A. G. Zagatto, Anal. Chim. Acta, 2002, 466, 125–132.

146 C. M. P. V. Lopes, A. A. Almeida, J. L. M. Santos andJ. L. F. C. Lima, Anal. Chim. Acta, 2006, 555, 370–376.

147 C. P�erez-Sirvent, M. J. Mart�ınez-S�anchez, M. Garc�ıa-Lorenzo,I. L�opez-Garc�ıa and M. Hern�andez-C�ordoba, Anal. Bioanal.Chem., 2007, 388, 495–498.

148 I. L�opez-Garc�ıa, J. Arroyo-Cortez and M. Hern�andez-C�ordoba,Talanta, 2008, 75, 480–485.

149 J. Ruzicka, Analyst, 2000, 125, 1053–1060.150 Y. L. Yu, Z. Du and J. H. Wang, J. Anal. At. Spectrom., 2007, 22,

650–656.151 P. Ampan, J. Ruzicka, R. Atallah, G. D. Christian, J. Jakmunee and

K. Grudpan, Anal. Chim. Acta, 2003, 499, 167–172.152 A.Manz, N. Graber andH.M.Widmer, Sens. Actuators, B, 1990, 1–

6, 244–248.153 T. Vilkner, D. Janasek andA.Manz,Anal. Chem., 2004, 76, 3373–3386.154 R. D. Johnson, V. G. Gavalas, S. Daunert and L. G. Bachas, Anal.

Chim. Acta, 2008, 613, 20–30.155 Q. J. Song, G. M. Greenway and T. McGreedy, J. Anal. At.

Spectrom., 2004, 19, 883–887.156 G. Pearson and G. Greenway, J. Anal. At. Spectrom., 2007, 22, 657–

662.157 H. Cheng, Z. Xu, J. Liu, X.Wang andX. Yin, J. Anal. At. Spectrom.,

2012, 27, 346–353.158 J. P. Lafleur and E. D. Salin, J. Anal. At. Spectrom., 2009, 24, 1511–

1516.159 B. Chen, S. Heng, H. Peng, B. Hu, X. Yu, Z. Zhang, D. Pang, X. Yue

and Y. Zhu, J. Anal. At. Spectrom., 2010, 25, 1931–1938.160 B. Chen, B. Hu, P. Jiang, M. He, H. Peng and X. Zhang, Analyst,

2011, 136, 3934–3942.161 C. Bendicho and M. T. C. de Loos-Vollebregt, J. Anal. At.

Spectrom., 1991, 6, 353–374.162 A. Martin-Esteban and B. Slowikowski, Crit. Rev. Anal. Chem.,

2003, 33, 43–55.163 M. G. R. Vale, N. Oleszczuk and W. N. L. dos Santos, Appl.

Spectrosc. Rev., 2006, 41, 377–400.164 B. Welz, M. G. R. Vale, D. L. G. Borges and U. Heitmann, Anal.

Bioanal. Chem., 2007, 389, 2085–2095.165 M. Resano, F. Vanhaecke andM. T. C. de Loos-Vollebregt, J. Anal.

At. Spectrom., 2008, 23, 1450–1475.166 M. Aramend�ıa, M. Resano and F. Vanhaecke, Anal. Chim. Acta,

2009, 648, 23–44.167 Z. Zaide, Z. Kaizhong, H. Xiandeng and L. Hong, Appl. Spectrosc.

Rev., 2005, 40, 165–184.168 F. L. King, J. Teng and R. E. Steiner, J. Mass Spectrom., 1995, 30,

1061–1075.169 D. G€unther, S. E. Jackson and H. P. Longerich, Spectrochim. Acta,

Part B, 1999, 54, 381–409.170 J. D. Winefordner, I. B. Gornushkin, D. Pappas, O. I. Matveev and

B. W. Smith, J. Anal. At. Spectrom., 2000, 15, 1161–1189.171 J. M. Vadillo and J. J. Laserna, Spectrochim. Acta, Part B, 2004, 59,

147–161.172 J. D. Winefordner, I. B. Gornushkin, T. Correll, E. Gibb,

B. W. Smith and N. Omenetto, J. Anal. At. Spectrom., 2004, 19,1061–1083.

173 D. G€unther and B. Hattendorf, TrAC, Trends Anal. Chem., 2005, 24,255–265.

174 C. Pickhardt, H. J. Dietze and J. S. Becker, Int. J. Mass Spectrom.,2005, 242, 273–280.

175 B. Fernandez, F. Claverie, C. Pecheyran and O. F. X. Donard,TrAC, Trends Anal. Chem., 2007, 26, 951–966.

176 J. Pisonero, B. Fernandez and D. G€unther, J. Anal. At. Spectrom.,2009, 24, 1145–1160.

177 B. Fern�andez, R. Pereiro and A. Sanz-Medel, Anal. Chim. Acta,2010, 679, 7–16.

178 K. Janssens, W. D. Nolf, G. V. D. Snickt, L. Vincze, B. Vekemans,R. Terzano and F. E. Brenker, TrAC Trends Anal. Chem., 2010, 29,464–478.


179 U. E. A. Fittschen and G. Falkenberg, Spectrochim. Acta, Part B,2011, 66, 567–580.

180 M. West, A. T. Ellis, P. J. Potts, C. Streli, C. Vanhoof,D. Wergrzynek and P. Wobrauschek, J. Anal. At. Spectrom., 2011,26, 1919–1963.

181 M. Resano, E. Garc�ıa-Ruiz, M. A. Belarra, F. Vanhaecke andK. S. McIntosh, TrAC, Trends Anal. Chem., 2007, 26, 385–395.

182 B. Bekhoff, B. Kanngießer, N. Langhoff, R. Wedell and H. Wolff,Handbook of Practical X-Ray Fluorescence Analysis, Springer, NewYork, 2006.

183 M. A. Zezzi Arruda, Trends in Sample Preparation, Nova SciencePublishers, New York, 2007.

184 L. Qi, J. Gao, X. Huang, J. Hu, M. F. Zhou and H. Zhong, J. Anal.At. Spectrom., 2011, 26, 1900–1904.

185 S. F. Boulyga and K. G. Heumann, Anal. Bioanal. Chem., 2005, 383,442–447.

186 J. D. Kerber, At. Absorpt. Newsl., 1971, 10, 104–105.187 www.analytik-jena.de/en/solid-AA/Systems-4400, last accessed June

2012.188 D. E. Nixon, V. A. Fassel and R. N. Kniseley,Anal. Chem., 1974, 46,

210–213.189 www.spectral-systems.de/english/autosamp.htm, last accessed June

2012.190 M. A. Belarra, M. Resano, F. Vanhaecke and L. Moens, TrAC,

Trends Anal. Chem., 2002, 21, 828–839.191 H. M. Ortner, E. Bulskab, U. Rohra, G. Schlemmerc,

S. Weinbruchd and B. Welz, Spectrochim. Acta, Part B, 2002, 57,1835–1853.

192 V. N. Oreshkin and G. I. Tsizin, J. Anal. Chem., 2011, 66, 951–954.193 X. Hou and B. T. Jones, Spectrochim. Acta, Part B, 2002, 57, 659–

688.194 M. L. Lin and S. J. Jiang, J. Anal. At. Spectrom., 2011, 26, 1813–

1818.195 M. A. Amberger and J. A. C. Broekaert, J. Anal. At. Spectrom.,

2010, 25, 1308–1315.196 G. Xiang, B. Hu and Z. Jiang, J. Mass Spectrom., 2006, 41, 1378–

1385.197 V. Thomsen and J. L. Spencer, Spectroscopy, 2011, 26, 18–21.198 V. Thomsen, Spectroscopy, 2010, 25, 44–45.199 www.angstrom-inc.com/spectrometers.html, last accessed June

2012.200 P. D. Pant, PCT Int. Appl., WO 2011114340 A2 20110922, 2011.201 F. Vincent, J. P. Sola and G. Wuethrich, Brit. UK Pat. Appl., GB

2466198 A 20100616, 2010.202 https://www.thermo.com/eThermo/CMA/PDFs/./productPDF_

57273.PDF, last accessed June 2012.203 A. F. Kiera, S. Schmidt-Lehr, M. Song, N. Bings and

J. A. C. Broekaert, Spectrochim. Acta, Part B, 2008, 63, 287–292.204 G. Buchbinder, N. Verblyudov and A. Clavering, Spectroscopy,

2009.205 J. Roy and L. Neufeld, Spectroscopy, 2004, 19, 16–28.206 T. D. F. Leite, R. Escalfoni Jr., T. C. O. da Fonseca and

N. Miekeley, Spectrochim. Acta, Part B, 2011, 66, 314–320.207 I. Konz, B. Fern�andez, M. L. Fern�andez, R. Pereiro and A. Sanz-

Medel, Anal. Bioanal. Chem., 2012, 403, 2113–2125.208 J. S. Becker, Int. J. Mass Spectrom., 2010, 289, 65–75.209 F. J. Fortes and J. J. Laserna, Spectrochim. Acta, Part B, 2010, 65,

975–990.210 A. Ciucci, V. Palleschi, S. Rastelli, A. Salvetti, D. P. Singh and

E. Tognoni, Laser Part. Beams, 1999, 17, 793–797.211 S. Palanco, A. Alises, J. Cu~nat, J. Baena and J. J. Laserna, J. Anal.

At. Spectrom., 2003, 18, 933–938.212 T. Nelis and J. Pallosi, Appl. Spectrosc. Rev., 2006, 41, 227–258.213 R. Pereiro, A. Sol�a-V�azquez, L. Lobo, J. Pisonero, N. Bordel,

J. M. Costa and A. Sanz-Medel, Spectrochim. Acta, Part B, 2011,66, 399–412.

214 M. J. Heintz and G. M. Hieftje, Spectrochim. Acta, Part B, 1995, 50,1109–1124.

215 G. P. Jackson, R. G. Haire and C. Duckworth, J. Anal. At.Spectrom., 2003, 18, 665–669.

216 L. Gao, Q. Song, R. J. Noll, J. Duncan, R. G. Cooks and Z. Ouyang,J. Mass Spectrom., 2007, 42, 675–680.

217 W. C. Davis, B. C. Knippel, J. E. Cooper, B. K. Spraul, J. K. Rice,D. W. Smith, Jr and R. K. Marcus, Anal. Chem., 2003, 75, 2243–2250.



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


218 T. M. Brewer, W. Clay Davis and R. K. Marcus, J. Anal. At.Spectrom., 2006, 21, 126–133.

219 D. Fliegel and D. G€unther, Spectrochim. Acta, Part B, 2009, 64, 399–407.

220 M. Tarik and D. G€unther, J. Anal. At. Spectrom., 2010, 25, 1416–1423.

221 E. Margu�ı, M. Hidalgo and I. Queralt, Spectrochim. Acta, Part B,2005, 60, 1363–1372.

222 G. Custo, S. Boeykens, L. Dawidowski, L. Fox, D. Gomez, F. Lunaand C. Vazquez, Anal. Sci., 2005, 21, 751–756.

223 N. Bukowiecki, P. Lienemann, C. N. Zwicky, M. Furger,A. Richard, G. Falkenberg, K. Rickers, D. Grolimund, C. Borca,M. Hill, R. Gehrig and U. Baltensperger, Spectrochim. Acta, PartB, 2008, 63, 929–938.

224 I. de la Calle, M. Costas, N. Cabaleiro, I. Lavilla and C. Bendicho,Spectrochim. Acta, Part B, 2012, 67, 43–49.

225 R. E. A. Jim�enez, Spectrochim. Acta, Part B, 2001, 56, 2331–2336.226 http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c¼ecfr&sid¼e29fdcb9d

258d1ed8c80f521ef9801a4&rgn¼div6&view¼text&node ¼ 42:5.0.1.1.5.3&idno ¼ 42, last accessed June 2012.

227 http://epswww.unm.edu/xrd/xrd_haz.pdf, last accessed June 2012.228 Environmental Protection Agency, USA, Environmental Technology

Verification Report: Field Portable X-Ray Fluorescence Analyzer,Spectrace TN 9000 and TN Pb Field Portable X-Ray FluorescenceAnalyzers, EPA/600/R-97/145, Washington DC, 1998.

229 J. Injuk, R. Van Grieken, A. Blank, L. Eksperiandova andV. Buhrke, in Handbook of Practical X-Ray Fluorescence Analysis,ed. B. Bekhoff, B. Kanngießer, N. Langhoff, R. Wedell and H.Wolff, Springer, New York, 2006, pp. 415–424.

230 R. B. Hallet and P. R. Kyle, Geostand. Newsl., 1993, 17, 127–133.231 S. Barrento, A. Marques, B. Teixeira, P. Vaz-Pires, M. L. Carvalho

and M. L. Nunes, Food Chem., 2008, 111, 862–867.232 M. F. Galluza, S. Vicente, M. Ordu~na and M. J. Ventura, X-Ray

Spectrom., 2012, 41, 176–185.233 C. Vazquez, G. Custo, N. Barrio, J. Bur�ucua, S. Boeykens and

F. Marte, Spectrochim. Acta, Part B, 2010, 65, 852–858.234 http://www.bruker-axs.com/artax.html, last accessed June 2012.235 G. Buzanich, P. Wobrauscheck, C. Streli, A. Markowicz,

D. Wegrzynek, E. Chine-Cano and S. Bamford, Spectrochim.Acta, Part B, 2007, 62, 1252–1256.

236 A. von Bohlen, Spectrochim. Acta, Part B, 2009, 64, 821–832.237 http://www.bruker-axs.com/s2picofox.html, last accessed June

2012\.238 http://www.bruker-axs.com/traceriiiv.html, last accessed June 2012.239 N. Forster, P. Grave, N. Vickery and L. Kealhofer, X-Ray

Spectrom., 2011, 40, 389–398.240 Y. Shibata, J. Suyama, M. Kitano and T. Nakamura, X-Ray

Spectrom., 2008, 38, 410–416.241 E. Margu�ı, C. Font�as, A. Buend�ıa, M. Hidalgo and I. Queralt, J.

Anal. At. Spectrom., 2009, 24, 1253–1257.242 A. A. Shaltout, B. Welz andM. A. Ibrahim,Microchem. J., 2011, 99,

356–363.243 A. J. Aller, Espectroscopia at�omica electrot�ermica anal�ıtica,

Secretariado de Publicaciones y Medios Audiovisuales de laUniversidad de Le�on, Le�on, 2003.

244 H. E. Taylor, Inductively Coupled Plasma-Mass SpectrometryPractices and Techniques, Academic Press, San Diego, 2001.

245 S. E. Maestre, J. L. Todol�ı and J. M. Mermet, Anal. Bioanal. Chem.,2004, 379, 888–899.

246 J. L. Todoli, V. Hernandis, A. Canals and J. M. Mermet, J. Anal. At.Spectrom., 1999, 14, 1289–1295.

247 F. Vanhaecke, M. V. Holderbeke, L. Moens and R. Dams, J. Anal.At. Spectrom., 1996, 11, 543–548.

248 S. F. Boulyga and J. S. Becker, Fresenius’ J. Anal. Chem., 2001, 370,612–617.

249 J. A. Koropchak and M. Veber, Crit. Rev. Anal. Chem., 1992, 23,113–141.

250 X. Zhang, D. Chen, R. Marquardt and J. A. Koropchak,Microchem. J., 2000, 66, 17–53.

251 N. Praphairaksit, D. R. Wiederin and R. S. Houk, Spectrochim.Acta, Part B, 2000, 55, 1279–1293.

252 J. A. C. Broekaert and V. Siemens, Anal. Bioanal. Chem., 2004, 380,185–189.

253 B. €Ozmen, F. M. Matysik, N. H. Bings and J. A. C. Broekaert,Spectrochim. Acta, Part B, 2004, 59, 941–950.


254 X. Guo, R. E. Sturgeon, Z. Mester and G. J. Gardner, Anal. Chem.,2004, 76, 2401–2405.

255 F. G. Bessoth, O. P. Naji, J. C. T. Eijkel and A. Manz, J. Anal. At.Spectrom., 2002, 17, 794–799.

256 J. A. C. Broekaert and U. Engel, in Encyclopedia of AnalyticalChemistry, ed. R. A. Meyer, John Wiley & Sons, Chichester, 2000,pp. 9613–9667.

257 J. Cai, in Encyclopedia of Analytical Chemistry, ed. R. A. Meyer,John Wiley & Sons, Chichester, 2000, pp. 2270–2292.

258 J. D�edina, Spectrochim. Acta, Part B, 2007, 62, 846–872.259 J. D�edina and T. Matou�sek, J. Anal. At. Spectrom., 2000, 15, 301–

304.260 W. T. Corns, P. B. Stockwell, L. E. Ebdon and S. J. Hill, J. Anal. At.

Spectrom., 1993, 8, 71–77.261 Y. Ogra, Biomed. Res. Trace Elem., 2008, 19, 34–42.262 R. Lobinski, D. Schauml€offel and J. Szpunar,Mass Spectrom. Rev.,

2006, 25, 255–289.263 Y. C. Sun, Y. C. Chang and C. K. Su, Anal. Chem., 2006, 78, 2640–

2645.264 H. Matusiewicz and R. E. Sturgeon, Spectrochim. Acta, Part B,

1996, 51, 377–397.265 O. Y. Ataman, Spectrochim. Acta, Part B, 2008, 63, 825–834.266 B. Doc�ekal, S. Gucer and A. Seleck�a, Spectrochim. Acta, Part B,

2004, 59, 487–495.267 X. D. Hou, K. E. Levine, A. Salido, B. T. Jones, M. Ezer, S. Elwood

and J. B. Simeonsson, Anal. Sci., 2001, 17, 175–180.268 B. Welz and M. Sperling, Atomic Absorption Spectrometry, Wiley-

VCH, Weinheim, 1999.269 B. Welz, S. Mor�es, E. Casarek, M. G. R. Vale, M. Okruss and

H. Becker-Ross, Appl. Spectrosc. Rev., 2010, 45, 327–354.270 J. Namie�snik, J. Sep. Sci., 2001, 24, 151–153.271 E. Marengo, M. Aceto, E. Robotti, M. Oddone and M. Bobba,

Talanta, 2008, 76, 1224–1232.272 Z. Jokai and P. Fodor, J. Anal. At. Spectrom., 2009, 24, 1229–1236.273 G. R. Lloyd, S. Ahmad, M. Wasim and R. G. Brereton, Anal. Chim.

Acta, 2009, 649, 33–42.274 K. Schaefer, J. W. Einax, V. Simeonov and S. Tsakovski, Anal.

Bioanal. Chem., 2010, 396, 2675–2683.275 M. J. Latorre, R. Pe~na, S. Garc�ıa and C. Herrero,Analyst, 2000, 125,

307–312.276 K. Ariyama, H. Horita and A. Yasui, Anal. Sci., 2004, 20, 871–877.277 R. Iglesias Rodr�ıguez, M. Fern�andez Delgado, J. Barciela Garc�ıa,

R. M. Pe~na Crecente, S. Garc�ıa Mart�ın and C. Herrero Latorre,Anal. Bioanal. Chem., 2010, 397, 2603–2614.

278 A. P. Fernandes, M. C. Santos, S. G. Lemos, M. M. C. Ferreira,A. R. A. Nogueira and J. A. Nobrega, Spectrochim. Acta, Part B,2005, 60, 717–724.

279 M. Costas-Rodriguez, I. Lavilla and C. Bendicho, Anal. Chim. Acta,2010, 664, 121–128.

280 M. Otto, Chemometrics. Statistical and Computer Application inAnalytical Chemistry, Wiley-VCH, Weinheim, 2007.

281 X. T. Morer, L. Gonzalez-Sabat�e, L. Fernandez-Ruano andM. P. Gomez-Carracedo, in Basic Chemometric Techniques inAtomic Spectroscopy, ed. J. M. Andrade, Royal Society ofChemistry, Cambridge, 2009, pp. 51–141.

282 M. Cocchi, C. Durante, A. Marchetti, M. Li Vigni, C. Baschieri,L. Bertacchini, S. Sighinolfi, L. Tassi and S. Totaro, inMicrowaves: Theoretical Aspects and Practical Applications inChemistry, ed. A. Marcheti and S. Sighinolfi, Transworld ResearchNetwork, T. C., Kerala, 2011, pp. 203–226.

283 J. M. O. Souza and C. R. T. Tarley, Int. J. Environ. Anal. Chem.,2009, 89, 489–502.

284 E. Kend€uzler, S. Baytak, €O. Yalcinkaya and A. R. T€urker, Can. J.Anal. Sci. Spectrosc., 2007, 52, 91–100.

285 S. L. C. Ferreira, S. M. Macedo, D. C. dos Santos, R. M. de Jesus,W. N. L. dos Santos, A. F. S. Queiroz and J. B. de Andrade, J. Anal.At. Spectrom., 2011, 26, 1887–1891.

286 F. Bianchi and M. Careri, Curr. Anal. Chem., 2008, 4, 142–151.287 D. B. Hibbert and N. Armstrong, Chemom. Intell. Lab. Syst., 2009,

97, 211–220.288 M. A. Bezerra, R. E. Santelli, E. P. Oliveira, L. S. Villar and

L. A. Escaleira, Talanta, 2008, 76, 965–977.289 J. M. Andrade, M. J. Cal-Prieto, M. P. G�omez-Carracedo,

A. Carlosena and D. Prada, J. Anal. At. Spectrom., 2008, 23, 15–28.



Publ

ishe

d on

04

Sept

embe

r 20

12. D

ownl

oade

d on

18/

06/2

015

14:2

9:54


290 C. Y. Fu, L. I. Petrich, P. F. Daley, A. K. Burnham and K. Alan,Anal. Chem., 2005, 77, 4051–4057.

291 T. Pettke, C. A. Heinrich, A. C. Ciocan and D. Gunther, J. Anal. At.Spectrom., 2000, 15, 1149–1155.

292 T. Nomizu, H. Hayashi, N. Hoshino, T. Tanaka, H. Kawaguchi,K. Kitagawa, K. Kuniyuki and S. Kaneco, J. Anal. At. Spectrom.,2002, 17, 592–595.

293 D. Q. Zhang, C.M. Li, L. L. Yang andH.W. Sun,Anal. Chim. Acta,2000, 405, 185–190.

294 I. Lopez-Garc�ıa, M. S�anchez-Merlos, P. Vi~nas and M. Hern�andez-Cordoba, J. Anal. At. Spectrom., 2001, 16, 1185–1189.

295 M. Felipe-Sotelo, J. M. Andrade, A. Carlosena and D. Prada, Anal.Chem., 2003, 75, 5254–5261.

296 X. Ma and Z. Zhang, J. Anal. At. Spectrom., 2004, 19, 738–742.297 E. S. Chaves, S. Compernolle, M. Aramendia, E. Javierre,

E. Tresaco, M. T. C. de Loos-Vollebregt, A. J. Curtius andF. Vanhaecke, J. Anal. At. Spectrom., 2011, 26, 1833–1840.

298 S. Prikler, D. Pick and J. W. Einax, Anal. Bioanal. Chem., 2012, 403,1109–1116.

299 J. M. Cottle, M. S. A. Horstwood and R. R. Parrish, J. Anal. At.Spectrom., 2009, 24, 1355–1363.

300 H. Yihua, T. Li, W. Xi, H. Xiandeng and L. Yong-Ill, Appl.Spectrosc. Rev., 2007, 42, 119–138.

301 S. Lahiri and M. J. Stillman, Anal. Chem., 1992, 64, 283A–291A.302 H. Ying, P. Yang, X. Wang and B. Huang, Spectrochim. Acta, Part

B, 1996, 51, 877–886.303 Z. Zhang and X. Ma, Curr. Top. Anal. Chem., 2002, 3, 105–123.


304 D. P. Webb and E. D. Salin, J. Anal. At. Spectrom., 1989, 4, 793–796.

305 P. Yang, H. Ying, X. Wang and B. Huang, Spectrochim. Acta, PartB, 1996, 51, 889–896.

306 C. Sartoros, J. F. Alary, E. D. Salina and J. M. Mermet,Spectrochim. Acta, Part B, 1997, 52, 1923–1927.

307 F. A. Settle Jr, B. I. Diamondstone, H. M. Kingston andM. A. Pleva, J. Chem. Inf. Model., 1989, 29, 11–17.

308 F. A. Settle Jr, P. J. Walter, H. M. Kingston, M. A. Pleva, T. Sniderand W. Boute, J. Chem. Inf. Model., 1992, 32, 349–353.

309 F. Klages and G. Wuensch, J. Prakt. Chem./Chem.-Ztg., 1996, 338,16–22.

310 G. Wuensch and F. Klages, J. Prakt. Chem./Chem.-Ztg., 1996, 338,593–597.

311 C. C. Huang, M. H. Yang and T. S. Shih, Anal. Chem., 1997, 69,3930–3939.

312 H. Ying, J. Murphy, J. W. Trompa, J. M. Mermet and E. D. Salina,Spectrochim. Acta, Part B, 2000, 55, 311–326.

313 B. van den Bogaert, J. B. W. Morsink and H. C. Smit, Anal. Chim.Acta, 1992, 270, 107–113.

314 B. van den Bogaert, J. B. W. Morsink and H. C. Smit, Anal. Chim.Acta, 1992, 270, 115–130.

315 D. Wienke, T. Vijn and L. Buydens, Anal. Chem., 1994, 66, 841–849.316 C. Pons, M. Mir�o, E. Becerra, J. M. Estela and V. Cerda, Talanta,

2004, 62, 887–895.317 M. I. G. S. Almeida, M. A. Segundo, J. L. F. C. Lima and

A. O. S. S. Rangel, J. Anal. At. Spectrom., 2009, 24, 340–346.



Date post:	06-Oct-2020
Category:	Documents
Upload:	others
View:	1 times
Download:	0 times

Green chemistry in analytical atomic spectrometry: a revie · Green chemistry in analytical atomic...

Documents