Chemical Modifiers Based on Platinum-Group Metal Compounds in Electrothermal Atomic Absorption Spectrometry

Abstract

Mechanisms of the action of chemical modifiers based on platinum-group metals have been considered. It has been shown that the efficiency of a chemical modifier is determined mainly by chemical processes occurring at the pyrolysis step. By combining the results obtained using different methods, these processes have been described step-by-step. The systematic study of Pd, Pt, Rh, Ru, and Ir in chloride and sulfate media as chemical modifiers has revealed a correlation between the relative efficiencies and some chemical properties of the modifiers. It has been shown that, in the presence of matrices weakly interacting with platinum-group metals (for example, sodium chloride), the best modifiers are metals that most intensely interact with the analytes (ruthenium and iridium in determining metalloids). However, if the chemical modifier strongly interacts with the sample matrix, the efficiency of the modifier is determined by the interaction processes. For example, in the presence of a sulfate matrix capable of reacting with platinum-group metals, the best modifier is palladium. The correlations found may be useful for the practical application of platinum-group metals as chemical modifiers in the analysis of complex samples by electrothermal atomic absorption spectrometry.