Comparative efficiency of Pd, Rh and Ru modifiers in electrothermal atomic absorption 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 graphite (THGA), the negative influence of the matrix was quite pronounced. The efficiencies of the platinum group metal (PGM) modifiers in this medium differ significantly. For Rh and Ru modifiers, some suppression of the analytical signals for Se and In is observed in the presence of as little as 0.1 µg and 1 µg of sulfate ion (as sodium sulfate), respectively. Moreover, for the Ru modifier, the maximum pyrolysis temperatures for As and In in the sulfate matrix decrease from 1200–1400 °C to 600 °C. In general, 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 modifier allows As and In to be determined almost interference free in the presence of up to 40 µg of sulfate ion (the corresponding value for Se is 20 µg). The differences in the effectiveness of the PGM modifiers seem to be caused mainly by the peculiarities of their interaction with the sulfate matrix. 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.