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DEVELOPMENT OF THE SOLID SAMPLING ETAAS METHOD FOR THE DETERMINATION OF TIN IN
SOILS AND THE COMPARISON WITH DISSOLUTION BASED LIQUID SAMPLING ETAAS
PÉTER TÖRÖK * and MÁRIA ŽEMBERYOVÁ
Comenius University in Bratislava, Department of Analytical Chemistry, Faculty of Natural Sciences, 842 15 Bratislava,
Slovak Republic
e-mail torok@fns.uniba.sk
1. Introduction
One of the most important properties of metals is their ability to accumulate in soils and other parts of environment.
For these reasons, special attention should be paid particularly to the analytical determination of environmentally relevant
elements. The analysis of soil samples is difficult task for the analytical chemist [1]. Total dissolution of soils requires
development of time-consuming procedures, which usually involve the use of hazardous reagents [2]. Moreover, depending
on the procedure selected, satisfactory results are not always guaranteed, due to the possible occurrence of analyte losses,
contamination or to an incomplete analyte recovery [3,4].
The direct determination of elements in solid samples by methods of atomic spectromery without prior digestion is in
many cases more efficient and reliable, faster, easier, more cost-effective and less time-consuming than other methods that
requires sample dissolution [5]. Therefore, the solid sample analysis using atomic absorption spectrometry with
electrothermal atomization (SS ETAAS) is a very promising trace analysis strategy [6]. Although it seems obvious that SS
ETAAS is a powerful technique it is rather limited by matrix effect of analyzed samples [7,8]. It can be mentioned that most
of the works published to date have dealt with situations in which the volatilities of the analyte and the matrix are very
different [9-13], while those situations in which the volatility of the analyte and the matrix are almost similar have been less
often promoted [14].
In the present work our intention was to develop rapid and simple solid sampling analytical method for direct
determination of tin in three different type of soils by ETAAS. Determination of Sn in environmental samples is problematic,
because of complicated chemical behavior of the analyte [15]. During decomposition a part of total Sn can lost as a volatile
SnCl 4 and the other part of analyte can be converted to the insoluble SnO2 by oxidizing mineral acids [16]. It is therefore
obvious that the development of solid sampling methods for the direct determination of Sn in soils would be covertable in
order to improve both the ability to obtain rapid results and the reliability of the results obtained. A study was carried out for
selection of the most appropriate working conditions: to study the use of alternative, less sensitive, resonance lines; selection
of the suitable chemical modifiers for achieving successful in situ analyte/matrix separation; the optimization of the sample
mass; to study the potential interferences and other adverse effects, and the ways for their elimination.
2. Experimental
2.1. Instrumentation
The solid sampling analysis were carried out using an AAS 5EA atomic absorption spectrometer (Analytik Jena AG,
Jena, Germany) equipped with a deuterium arc background correction and transversely heated graphite tube atomizer
(THGA). A laboratory made device was used for direct sample introduction. Hollow cathode lamp (Photron Pty. Ltd.,
Australia) was the line source (wavelength 300.9 nm, spectral band pass 0.5 nm, lamp current 7.5 mA) during Sn
determination. Pyrolytically coated graphite tubes without dosing hole (Analytik Jena AG, Jena, Germany) and pyrolytically
coated graphite platforms (Analytik Jena AG, Jena, Germany) designed for solid sampling, were used for all experiments. An
M500P ultra-micro balance (Sartorius, Goettingen, Germany) was used for weighing the samples directly into the solid
sampling platforms. To obtain the same heating conditions with solid samples, the aqueous standards were pipetted manually
on to the same platforms as solid samples. Aqueous standards and modifiers were pipetted by a variable Eppendorf
micropipette (maximum pipettable volume 200 L). Precision of micropipette and microbalance are ±0.5 L and ±0.005 mg,
respectively. High purity argon (99,999%) was used as the purge gas with maximum flow rate of 1 2 L.min -1 during all
stages, except auto zero and atomization, when gas flow was reduced to 0.1 L min -1 . Established optimum working
conditions and furnace heating program for direct determination of tin in soil samples is presented in Table 1, the same
optimized heating program can be applied for analysis of all reference materials. Quantification of Sn in solid samples was
performed by calibration against aqueous standards, which were pipetted onto the matrix residue remaining from a previous
sample run.
The analysis of digested samples was performed on a Perkin-Elmer (Norwalk, CT, USA) model 1100B atomic
absorption spectrometer with deuterium arc background correction, equipped with an HGA-700 graphite furnace, and an AS-
60 autosampler. Pyrolytically coated HGA graphite tubes (Perkin-Elmer, USA) with preinserted pyrolytic platforms were
employed. An electrodeless discharge lamp (Perkin-Elmer, USA) operating at 8 W was used as radiation source. The 286.3
nm resonance line of Sn was used for the analysis (spectral band pass of 0.7 nm) which is actually not the most sensitive
wavelength. The reason for using the less sensitive wavelength was that the concentration of tin in samples was relatively
Zborník príspevkov
z 18. medzinárodnej vedeckej konferencie
"Analytické metódy a zdravie loveka", ISBN 978-80-969435-7-9
- 41 -
hotel Falkensteiner, Bratislava
11. - 14. 10. 2010