Investigation of sulfur release in ETV-ICP-AES and its application for the determination of sulfates |
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Authors: | Antje Mroczek Gerhard Werner R Wennrich Werner Schrön |
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Institution: | (1) University of Leipzig, Faculty of Chemistry and Mineralogy, Institute for Analytical Chemistry, Linnéstrasse 3, D-04103 Leipzig, Germany, DE;(2) UFZ, Centre for Environmental Research Leipzig-Halle Ltd., Dept. Analytical Chemistry, Permoserstrasse 15, D-04318 Leipzig, Germany, DE;(3) University of Jena, Faculty of Chemistry and Geoscience, Institute of Inorganic and Analytical Chemistry, Lessingstrasse 8, D-07743 Jena, Germany, DE |
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Abstract: | Electrothermal vaporization inductively coupled plasma atomic emission spectrometry was applied to the determination of sulfur
species in aqueous solutions. The sensitivity for sulfur as sulfate was found to be depending on the cations in the sample.
For understanding this phenomenon the thermal behavior of sulfuric acid, ammonium sulfate and the sulfates of sodium, zinc,
magnesium and silver was studied. There were significant differences in the thermal release of sulfur from these sulfates.
To explain these phenomena different reaction mechanisms were calculated using thermodynamic data. Pd(NO3)2 and Ge in KOH were successfully applied as modifiers for the stabilization of the sulfates during the thermal pre-treatment
step and to establish a uniform thermal behavior of different sulfates. The stabilization of sulfur using Ge and Pd as modifiers
is based on the reduction of the sulfates in presence of carbon, resulting in the formation of GeS and PdS, respectively.
This explanation has been supported by comparing the experimental results with thermodynamic calculations considering different
reactions for the thermal decomposition of the sulfates. Applying Ge (in KOH) as modifier the absolute detection limit was
300 pg sulfur (e.g. LOD 30 ng mL–1). The significant influence of phosphates on the determination of sulfur could be essentially reduced by Pd as modifier.
Received: 11 November 1997 / Revised: 14 January 1998 / Accepted: 18 January 1998 |
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