Comparative efficiency of Pd, Rh and Ru modifiers in electrothermal atomicabsorption spectrometry for the simultaneous determination of As, Se and In in a sodium sulfate matrix

The efficiency of pre-reduced Pd, Rh and Ru modifiers for the simultaneous determination of As, Se and In in a sodium sulfate matrix was investigated. In spite of the application of an isothermal atomizer transverse heated gr aphite (THGA), the negative influence of the matrix was quite pronounced. T he efficiencies of the platinum group metal (PGM) modifiers in this medium differ significantly. For Rh and Ru modifiers, some suppression of the anal ytical signals for Se and In is observed in the presence of as little as 0. 1 mug and 1 mug of sulfate ion (as sodium sulfate), respectively. Moreover, for the Ru modifier, the maximum pyrolysis temperatures for As and In in t he sulfate matrix decrease from 1200-1400 degreesC to 600 degreesC. In gene ral, Rh and Ru modifiers are ineffective for the determination of As and In in a sodium sulfate matrix. The application of a pre-reduced palladium mod ifier allows As and In to be determined almost interference free in the pre sence of up to 40 mug of sulfate ion (the corresponding value for Se is 20 mug). The differences in the effectiveness of the PGM modifiers seem to be caused mainly by the peculiarities of their interaction with the sulfate ma trix. Therefore we suppose that the effects found in this work will also be important for the determination of other analytes in sulfate medium in the presence of PGM modifiers.