G.Bauer*, S. Smetaczek*, A.Limbeck*

* Vienna University of Technology, Institute for Chemical Technologies and Analytics, Getreidemarkt 9/164-IAC, 1060 Vienna, Austria

SPATIALLY RESOLVED ANALYSIS OF SINGLE PARTICLES USING LA-ICP-MS

METAL-CORE

PARTICLE

INTRODUCTION

Fly ash particulate matter is rich in heavy metals and is therefore a potential resource for recycling but also a potential source for

environmental pollution. So far state of the art treatment methods for municipal solid waste incineration (MSWI) bottom ash only remove

coarse metals. Regarding highly toxic MSWI fly ashes, industrial scale decontamination technologies are not available yet. Knowledge

on the distribution of metals within fly ash particles will help to find optimal treatment techniques and parameters (including use of

additives) for the decontamination process.

In this work we present a procedure to distinguish metal-core from metal-shell particles originating from powdered samples with

LA-ICP-MS. METAL-SHELL

CARBON-CORE PARTICLE

ABLATION TECHNIQUES

2.) PLANE ABLATION MODE

no wall effects

strong fixation

necessary

3.) PLANE ABLATION with subsequent

LINE SCANS no wall effects

2D-plane results

strong fixation

necessary

more effort

The deposition characteristics were investigated

by optical microscopy. Distribution on the

sample holders and deposited size fractions were

adjusted to prevent agglomerates and to depict

the sample composition representatively by

modifying parameters such as Ar gas flow, the

angle of dispersion on the sticky medium of

choice and amount of sample used in one

experiment.

Images were provided by a DM4000 microscope

from Leica equipped with high resolution

camera.

OUTLOOK

Further optimization of fixation process

Extending the variety of measured samples

2D-imaging of particles

CONCLUSION

For fixation the application of

hairspray proved to be most

efficient.

For LA-ICP-MS measurement

the third approach (plane

ablation with subsequent line

scans) showed the best results.

Metal-core and metal-shell

particles could be properly

discriminated with this

technique.

INSTRUMENTAL – Laser Ablation

For LA the NWR213 Laser Ablation system from ESI was

used.

Operation parameters were optimized regarding beam

diameter (10 – 50 µm), pulse rate (1 – 20 Hz),

laser energy (30 – 70 %), scan speed (5 – 20 µm/s) and gas

flow (transport line).

PARTICLE FIXATION APPROACHES

2.) EPOXY RESIN

good fixation,

on or just below

resin surface

only a fraction of

particles accesible

Particles are deposited on an

almost completely polymerized

epoxy resin.

1.) STICKY TAPE

light fixation

adhesive force

decreases with

Au coating

Particles are dispersed by

a regulated Ar gas stream

and deposited on a sticky

tape. The tape is coated

with a Gold thin layer

prior to particle addition.

3.) HAIRSPRAY

good fixation,

gold coating

possible

multiple layers

possible

A glass slide is coated with a Gold thin layer. Afterwards

common hairspray is used to prepare the sticky medium.

Plane ablation with

subsequent line scans:

Presence of metal-shell

particles could be verified

reproducibly.

Plane ablation mode:

Parallel removal of

sample and sticky

medium as well as Gold

coating obliterates

distinct depth layer

information.

Drilling mode:

Subsequent removal

of wall components

prevents depth layer

profiling for target

particles.

INSTRUMENTAL – ICP-MS

The ICP-MS used was the

iCAP Q from Thermo.

Alongside standard tuning

procedures, RF generator

power and carrier gas flow

were optimized to maximize

analyte sensitivity.

1.) DRILLING MODE

only light

fixation

necessary

wall effects

SAMPLES and PREPARATION

The samples originated from the Vienna community heating

combustion plant:

sample 1: FLA – fly ash d (0.9) = 97 µm

sample 2: KSA – sludge ash d (0.9) = 89 µm

sample 3: Schlacke – bed ash d (0.9) = 107 µm

The particle size distribution of each sample was analyzed using a Mastersizer 2000 (Malvern Industries,

England).

The powdered samples were prepared for measurement by dispersion with a regulated Ar gas stream in a

self-made glass apparatus with flow characteristics similar to a cyclone chamber. Regarding of the approach

the particles were deposited on glass slides prepared with sticky tape, resin or hairspray.

RESULTS

Investigated elements: Al, Si, Ti, Mn, Co, Ni, Cu, Zn,

Au and Pb