NEW APPROACH IN THE FIELD OF PREPARATION OF … · • checking the characteristics and application...

Jacek Namieśnik, Piotr Konieczka, Anna Świtaj-Zawadka

Department of Analytical Chemistry, Chemical Faculty Gdansk University of Technology

11/12 G. Narutowicza Str., 80-952 Gdańsk, POLANDe-mail: [email protected]

NEW APPROACH IN THE FIELD OF PREPARATION OF REFERENCE

MATERIALS OF VOLATILE MEASURANDS

2

The preparation of proper reference materials used in process of analysis of gaseous samples is a

particularly difficult task.


NEW APPROACH IN THE FIELD...

3

• calibration of the measuring and controlling devices;

• checking the characteristics and application range, it means validation, of new analytical procedures;

• checking the qualifications of the analytical personnel;

• inter-laboratory measurements and inter-calibrations;

• studies of:

GASEOUS STANDARD MIXTURES



- kinetics of different types of reactions occurring in agaseous phase;

- efficiency of new catalysts and sorbents;

4

GENERATION OF GASEOUS STANDARD MIXTURES

STATIC DYNAMIC

a known amount of pure gas or vapour is added to a known

volume of diluent gas in closed containers

stream of pure gas or vapour at a known flow-rate is

introduced continuously into a diluent gas stream



CLASSIFICATION OF TECHNIQUES OF GENERATION OF GASEOUS STANDARD

MIXTURES

5

GENERATION OF GASEOUS STANDARD MIXTURES

STATIC DYNAMIC

Pressurized AtmosphericPressure

gravimetric

volumetric

partial pressure

single fixed volume

chamber

multiple fixed volume

chambers

injection

variable volume

chambers

gas stream mixing

diffusion

evaporation

permeation

electrolytic

chemical reaction

autodilutionexponential dilution



6

MAIN PROBLEMS



adsorption of analytes on the walls of vessels and tubings -wall memory effect;

change of the composition of the mixtures;

technical problems with appropriate homogenisation of the mixture and resulting danger of stratification;

necessity of providing the matrix of the standard mixture asclose as possible to that of real samples;

difficulties in assuring the same way of supply of both thestandard mixture and the real sample to the detector;

occurrence of so called “ghost-peaks”;

7

TRENDS IN PREPARATION OF GASEOUS STANDARD MIXTURES



THERE IS NO IDEAL SOLUTION

IN THIS FIELD

8

TYPES OF REFERENCE MATERIALS OF ORGANIC MEASURANDS USED IN STUDIES OF

GASEOUS SAMPLES



- gaseous standard mixtures prepared by use one of known static techniques- as a result, gaseous mixtures in suitable containers are commercially available;

- gaseous standard mixtures prepared by use one of known dynamic techniques- in this case a special generators for production of stream of measurand in the stream of inert diluting gas are commercialised;

- sorption tubes- containing for example active carbon bed spiked with suitable amounts of organic measurands;

- solvent solutions of analytes- this technique can be applied only for non-volatile components.

9

MAIN DRAWBACKS OF KNOWN TECHNIQUES OF PREPARATION OF REFERENCE MATERIALS OF VOLATILE ORGANIC MEASURANDS

NEEDED FOR STUDIES OF GASEOUS SAMPLES



- need of derivatization of analytes (to prolonge thestability of standard life time;- problems with changes in composition of the standard mixture due to evaporation of volatile solvent.

Standard solutions

- necessity of storage in lowered temperature (to reduce migration and desorption process);- need of high purity solvent (at the step of elution of measurands;- non-quantitative desorption of measurands;

Sorbent tubes spiked with analyte(s)

- necessity of possesing of suitable source of measurand and generator;- need of precise control of the diluent gas flow rate;- difficulties with „stopping” process of generation of a stream of measurand in generator;

Standard gaseous mixtures

(generation of a stream of measurand(s) and

mixing with a stream of diluent gas)

- adsorption-desorption process (wall memory effect);- stratification components of mixtures (at the stage of storage);- not suitable for unstable or/and reactive components;

Standard gaseous mixtures

(in containers)

Drawbacks and disadventages/ main sources of errors

Type of reference material

10

NEW APPROACH IN THE FIELD OF GENERATION OF STANDARD GASEOUS MIXTURES



Suitable surface compounds are obtained by chemical modification

of the surface of solid support.

11

THE PRINCIPLES OF GASEOUS STANDARD MIXTURES PREPARATION WITH THE USE

OF THERMAL DECOMPOSITION OF SURFACE COMPOUNDS



During the chemical reaction, initiated by the adequately high

temperature, a surface compound decomposes or undergoes

transformation. It is followed by liberating of one or more volatile

chemicals of a precisely known identity.

12

SUPPORT MATERIALS FOR SURFACE COMPOUNDS



• homogenous and/or spherical shape of the particles within anarrow size range;

• uniform distribution of active sites on the surface;

• precisely defined porosity;

• high mechanical strength;

13

SOLID SUPPORTS FOR SURFACE COMPOUNDS



• silica gels;

• porous glasses;

• glass fibres;

14

gaseous standardmixture

SiOHSiOHSiOH

SiOHSi-YXSiOH

SiOHSi-YSiOH

¦¦

modifier XYseveral steps

chemical modification procedure

procedure of generation of standard gaseous mixture

carrier gastemperature

+ X in carrier gas detector

calibration step

measurand

GENERATION OF GASEOUS STANDARD MIXTURE BY THERMAL DECOMPOSITION OF SURFACE COMPOUND

OBTAINED ON THE SURFACE OF SILICA GEL



15

PREPARATION OF STANDARD GAS MIXTURES

STATIC DYNAMIC

Pressurized AtmosphericPressure

gravimetric

volumetric

partial pressure

single fixed volume

chamber

multiple fixed volume

chambers

injection

variable volume

chambers

gas stream mixing

diffusion

evaporation

permeation

electrolytic

chemical reaction

autodilutionexponential dilution

thermal decomposition of surface compounds



16

CONTROL OF THE MEASURAND AMOUNT GENERATED DURING THE PROCESS OF

THERMAL DECOMPOSITION



• mass of the modified support material sample;

• type and geometry of the support material;

• temperature at which decomposition takes place;

• flow-rate of a diluting gas through the generator of the gaseous mixture;

• duration of the gaseous standard mixture generation process;

17

EVALUATION OF THE SUITABILITY OF MATERIALS WITH CHEMICALLY MODIFIED

SURFACE FOR THE GENERATION OF GASEOUS STANDARD MIXTURES



1. Material purity2. Determination of decomposition temperature range3. Surface coverage homogeneity

18

SUPPORT MATERIAL PURITY



only needed substances are released from thesurface of the modified support

19

DECOMPOSITION TEMPERATURE RANGE

The temperature of decomposition should be much higher than ambient temperature; otherwise a standard in an immobilized formcannot be stored for a long time without analyte losses.



0

0,5

1

1,5

2

2,5

3

The

amou

nt o

f ac

etal

dehy

de

liber

ated

per

uni

tm

ass

[mg/

g]

130 140 150 160 170 180 190

Te mpe rature [o C]

20Jacek Namieśnik, Piotr Konieczka, Anna Świtaj-Zawadka


First of all, the amount of liberated compound per unit of mass of modified support material to the mass of the sample of modified material should be constant.

SURFACE COVERAGE HOMOGENITY

y = -0,32x + 2,90r = 0,61

0

0,5

1

1,5

2

2,5

3

3,5

0 1 2 3 4

Mass of silica gel used [mg]

Am

oun

t of

ace

tald

ehyd

e lib

erat

ed

per

mas

s u

nit

[mg/

g]

21

0.610.67

Correlation coefficient: ValueCritical value

2.31Critical t-Student value

-0.322.340.14

Slope - a : ValueStandard deviation

Calculated t-Student value

2.902.440.12 calculated as:

Intercept - b: ValueStandard deviation


2.60 ± 0.130.21

Average amount [mg·g-1]Standard deviation [mg·g-1]

Silica gelSupport

y=ax+bEquation

AcetaldehydeMeasurand

STATISTICAL EVALUATION



22

Secondly, the amount of liberated compound should be proportional to the mass of sample of chemically modified support.



SURFACE COVERAGE HOMOGENITY

y = 1.86x + 0.68r = 0.99

0

2

4

6

8

0 1 2 3 4

Mass of sil ica gel sample used [mg]

The

amou

nt o

f ac

etal

dehy

de [u

g]

23

0.990.67

Correlation coefficient: ValueCritical value

2.31Critical t-Student value

1.860.247.75

Slope - a: ValueStandard deviation


0.681.150.59

Intercept - b: ValueStandard deviation


Silica gelSupport

y=ax+bEquation

AcetaldehydeMeasurand

STATISTICAL EVALUATION



24

APPLICATION OF THE PROPOSED TECHNIQUE OF GENERATION OF GASEOUS STANDARD

MIXTURES

Depending on:

• the type of the detector used;

• the technique of mixture generation;

calibration can be performed in different mode.



25

carrier gas

detector

time of mixture generation

sign

al o

f det

ecto

r

CALIBRATION IN ON-LINE MODE



26

mass of modified support

detector

sign

al o

f det

ecto

r

carrier gas

trap

CALIBRATION IN OFF-LINE MODE(SINGLE-POINT OPTION)



27

carrier gas

detector

period of time of mixture generation

sign

al o

f det

ecto

r

CALIBRATION IN OFF-LINE MODE(MULTI-POINT OPTION)



28

carrier gas

detector

period of time of mixture generation

sign

al o

f det

ecto

r

CALIBRATION IN OFF-LINE MODE(MULTI-POINT OPTION)





CONCENTRATION OF AN ANALYTE IN THE MIXTURE

• the concentration of the analyte is known at any momentduring generation (in the case of “on-line” mode);

• the amount of the analyte generated in a given period of time is very well known (in the case of “off-line” mode);

30

Silica Gel

NDIR- Non-Dispersive Infrared DetectorFID- Flame Ionization Detector

250NDIR44 ± 1.565 ± 1.6

COCO2

300FID4.2 ± 0.10 [µg·cm-1]15.0 ± 0.33 [µg·cm-1]

COCO2

glass rods

300FID1.9 ± 0.212.7 ± 0.12

COCO2

250NDIR41 ± 1.2CO2

Temperature [°C]

Calibrated Detector

The amount ofa measurand [mg·g-1]

Measurand

FIELD OF APPLICATION OF THE PROPOSED TECHNIQUE



31

Silica Gel

320NPD3.1 ± 0.14(C2H5)2NH

3404.04 ± 0.090(C2H5)3N

3203.13 ± 0.036(C2H5)2NH

3101.57 ± 0.032CH3NH2

200

FID

1.21 ± 0.023NH3

1802.6 ± 0.13CH3HO

270FID3.40 ± 0.081CH3Cl

245FID0.48 ± 0.0015C2H4

Temperature [°C]

Calibrated Detector


Measurand

NPD- Nitrogen/ Phosphorus Detector

Phot

omet

ric D

etec

tor-

SQ 1

18 (

afte

r ab

sorp

tion

in s

olut

ion)




32

Silica Gel

Temperature [°C]

Calibrated Detector


Measurand

170MS420 ± 12 [ng·g-1]C3H7SH

150FPD15.5 ± 0.76C3H7SH

150FID17.4 ± 0.57C3H7SH

150FID13.2 ± 0.67CH3SH

150FID6.5 ± 0.29C4H9NCS

150FID5.2 ± 0.014CH2CHCH2NCS

FPD- Flame Photometric DetectorMS- Mass Spectrometer




33

Porous Glass and Glass Fibre

Temperature [°C]

Calibrated Detector


Measurand

2.24 ± 0.032

C2H4

245FID0.743 ± 0.0028[ng·cm-1 of glass fibre]

0.319 ± 0.0066

0.399 ± 0.012

210FID4.18 ± 0.036

C2H4




34

ADVANTAGES OF THE PROPOSED TECHNIQUE



1. Easy and direct determination of the amount of particular

gaseous analyte on the basis of known quantity of support

with chemically modified surface.

2. The possibility of generation of analyte during the

calibration process, which reduces the memory effect

associated with adsorption of compounds on the walls of

apparatus and tubings.

3. The high stability of modified materials at room

temperature.

35

ADVANTAGES OF THE PROPOSED TECHNIQUE (continued)



4. A wide range of concentration of the analyte in a diluent gas

is easily accessible by varying the parameters of the thermal

decomposition process (temperature, mass and capacity of

the gel sample and the flow rate of the diluent gas).

5. The suitability for generation of gaseous standard mixtures of

toxic, reactive, unstable and malodorous components.

6. The possibility of obtaining of measurands in gaseous

mixtures at the concentration level close to the detection limit

of calibrated instrument.

36

Bibliography



1. P. Konieczka, J. Namieśnik, and J.F. Biernat, J. Chromatogr., 540, 449 (1991).2. P. Konieczka, E. Luboch, J. Namieśnik, and J.F. Biernat, Anal. Chim. Acta, 265,

127 (1992).3. P. Konieczka, J. Makarewicz, E. Luboch, J. Namieśnik, and J.F. Biernat, Chem.

Anal., (Warsaw), 39, 179 (1994).4. P. Konieczka, J. Namieśnik, A. Przyjazny, E. Luboch, and J.F. Biernat, Analyst,

120, 2041 (1995).5. P. Konieczka, L. Wolska, E. Luboch, J. Namieśnik, A. Przyjazny, and J.F. Biernat,

J. Chromatogr. A, 742, 175 (1996).6. P. Konieczka, M. Prokopowicz, A. Skwierawska, A. Przyjazny, J.F. Biernat, and J.

Namieśnik, Mikrochim. Acta, 127, 211 (1997).7. M. Prokopowicz, K. Lewandowska, A. Skwierawska, A. Przyjazny, J.F. Biernat

and J. Namieśnik, Chromatographia, 44, 484 (1997).8. M. Prokopowicz, E. Luboch, J. Namieśnik, J.F. Biernat, and A. Przyjazny, Talanta,

44, 1551 (1997).9. M. Prokopowicz, A. Przyjazny, J.F. Biernat, and J. Namieśnik, Microchem. J., 59,

437 (1998).

37

10. M. Prokopowicz, E. Luboch, A. Przyjazny, J.F. Biernat, and J. Namieśnik, JHRC, 21, 303 (1998).

11. M. Prokopowicz, P. Konieczka, and J. Namieśnik, Environ. Technol., 20, 1065 (1999).

12. J.F. Biernat, M. Prokopowicz, P. Konieczka, J. Namieśnik, E. Luboch, and A. Skierawska, Biocyb. Biomed. Eng., 19, 5 (1999).

13. P. Konieczka, M. Prokopowicz, B. Zygmunt, J.F. Biernat, and J. Namieśnik, Chromatographia, 51, 249 (2000).

14. P. Konieczka, Fresenius. J. Anal. Chem., 367, 132 (2000).15. E. Przyk, P. Konieczka, J. Szczygelska-Tao, R. Teschner, J.F. Biernat, and J.

Namieśnik, J. Chromatogr A., 928, 99 (2001).16. E. Przyk, P. Konieczka, J. Szczygelska-Tao, J.F. Biernat, and J. Namieśnik, J.

Sep. Sci., 24, 226 (2001).17. A. Świtaj, E. Przyk, J. Szczygelska-Tao, J. Wójcik, J.F. Biernat, B. Zygmunt, and

J. Namieśnik, J. Sep. Sci., 26, 1057 (2003) .18. E. Przyk, A. Świtaj-Zawadka, P. Konieczka, J. Szczygelska-Tao, J.F. Biernat, and

J. Namieśnik, Anal. Chim. Acta, 448, 89 (2003).



Bibliography

38

ACKNOWLEDGEMENTS



This new approach is the fruit of close cooperation of our team with two scientific groups headed by:

- Professor J.F.Biernat - Department of Chemical Technology,Chemical Faculty of the Gdansk University of Technology

chemical modification of the surface of different type of solid supports

- Dr J. Wójcik - Laboratory of Optical Fibres Technology, Faculty of Chemistry, University of Maria Sklodowska-Curie in Lublin

preparation of suitable, fit for purpose, glass fibres

39

TRAP-NAS- TRAINING ON THE PRODUCTION AND USE OF REFERENCE MATERIALS IN NEWLY ASSOCIATED STATES

VI-RM- THE EUROPEAN VIRTUAL INSTITUTE FOR REFERENCE MATERIALS

QUA-NAS- IMPROVING THE INFRASTRUCTURE FOR METROLOGY IN CHEMISTRY IN THE CANDIDATE NEW MEMBER STATES



PARTICIPATION IN GRANTS FINANCED BY THE EUROPEAN COMMUNITY



CENTRE OF EXCELLENCE

Since January 1st, 2003 the Centre of Excellence in the field of environmental analytics and monitoring (CEEAM), financed by the European Community, has been operating. The Centre is based on the human and technical potential available at the Department ofAnalytical Chemistry from the Chemical Faculty of the Gdansk University of Technology.

An important part of the activities conducted at the Centre consists of research in the field of chemical metrology and reference materials.

www.pg.gda.pl/chem/CEEAM



42

THANK YOU FORYOUR ATTENTION

Date post:	10-Jun-2018
Category:	Documents
Upload:	ngotuyen
View:	213 times
Download:	0 times

NEW APPROACH IN THE FIELD OF PREPARATION OF … · • checking the characteristics and application...

Documents