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INTRODUCTION
Coal fly ash is known for its enriched metal contents but was studied mostly in the field of pollution monitoring and
influences on the ecological system [1]. Our goal is to examine the possible recycling potential by determining the
contents of target elements, usually metals like Au, Pt or U, which are present in trace concentration levels. Due to its
harsh matrix properties, fly ash analysis is a challenging topic, usually demanding intensive sample pre-treatment.
Typically some kind of digestion step is involved to separate the organic matrix. These approaches are labor and time
demanding and propose the risk of sample-contamination during pre-treatment, furthermore sample dilution
accomplished during sample digestion hampers sensitive measurement of target analytes.
BCR® - 176 R from
EC-JRC-IRMM and
was applied to fly ash
samples originating
from the Vienna
community heating
combustion plant.
In this work, an ETV-based method for direct, fast and accurate ICP-MS-analysis of trace elements and noble
metals is proposed. Sample preparation is reduced to simple dispersion of the particulate sample in diluted nitric acid.
An aliquot of the derived slurry solution is transferred to a graphite-boat and introduced to an electro thermal
vaporization unit coupled to an ICP-MS. The developed method was validated using certified reference material.
MS Parameters
ICP-MS measurements were carried
out on a Thermo iCAP ICP-MS.
Analyte masses were chosen
according to their abundance,
possible interferences and to the
quality of their respective calibration
curve (Co59, Ni60, Cd111, In115,
Pt195, Au197, Tl205, U238).
EXPERIMENTAL
Analytical procedure
• the fly ash samples were dispersed (concentration < 1 mg/10 ml) in 1% (v/v) nitric acid and engaged in a slurry state by means of a vortexer and ultrasonic agitation
• 20 µl of slurry solution were transferred into a graphite boat and the solvent was slowly evaporated by means of an IR-Lamp
• the graphite boat was planted into the ETV-4000 graphite furnace (Spectral Systems, Germany) an a temperature program (see Figure I) was applied.
•Analytes were transferred from ETV 4000 to ICP-MS and emission signals were recorded in transient signal mode (intensity vs. time).
G.Bauer*, A Limbeck*
* Vienna University of Technology, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-IAC, 1060 Vienna, Austria
ACCURATE ANALYSIS OF TRACE METALS IN FLY ASH
USING ELECTRO-THERMAL–VAPORISATION
IN COMBINATION WITH ICP-MS DETECTION
Figure I: optimized temperature program
0
500
1000
1500
2000
2500
0 20 40 60 80 100
tem
per
atu
re [
°C]
time [s]
Table I:
instrument parameters
RF power [W] 1200
plasma gas flow rate [L/min] 13
nebulizer flow rate [L/min] 0.52*
auxiliary flow rate [L/min] 0.8
Freon modifier [mL/min] 10
*sum of carrier gas and cooling gas
SAMPLES
The samples originated from the Vienna community heating combustion plant:
sample 1: FLA – fly ash
sample 2: KSA – sludge ash
sample 3: Schlacke – bed ash
Table II:
correlation between ICP-MS analysis
and SRM certified values
[mg/kg] Co
SRM certified concentration 26.7
± 1.6
Results ICP-MS analysis 27.0
± 1.0
METHOD VALIDATION
Standard reference material SRM BCR
176R was used
• to evaluate the signal quantification
and
• to test the accuracy of the method
OUTLOOK
Quantification of Gold and Uranium
Validation of ETV-ICP-MS analysis with
REE CRM
Expanding the number of analytes
REFERENCES
[1] Michaela Kröppl, Irene Lahoz Muñoz, Michaela Zeiner,
Toxicological & Environmental Chemistry, 93:5, 886-894 (2011)
[2] M. Resano, F. Vanhaecke and M. T. C. de Loos-Vollebregt, J. Anal.
At. Spectrom., 23, 1450–1475 (2008)
sample dispersion
IR-pre-drying
Temperature program
Atomization and ionization
Mass filter
Transient signal detection
iCAP Q (Thermo Scientific)
ETV 4000 (Spectral Systems)
Figure II: Transient signals and peak shapes in ETV-ICP-MS, Pt (green), U (pink) and Au (blue)
RESULTS
The presence of Uranium was confirmed for the all samples. Comparing the sample
results against each other the following relation was found:
KSA:FLA:Schlacke = 100:20:65
Small amounts of Gold are found in all samples but are still at or below LOD
(see Table II). Results for Co and Pt are displayed in Table III.
Table II ETV-ICP-MS
RSDs (n = 4): 3 %
[ng/boat] Au Co Pt
LOD (3 σ) 0.090 0.036 0.70
LOQ (10 σ) 0.099 0.043 0.82
Table III ETV-ICP-MS
RSDs (n = 3): < 10 %
[mg/kg] Au Co Pt
KSA < LOD 236 ± 18 32.7 ± 1.0
FLA 40.7 ± 0.4 319 ± 28 37.6 ± 1.0
Schlacke < LOD 409 ± 40 41.5 ± 3.9