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
