An investigation of different modifiers in electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS)

The suitability of eleven modifiers (Pd-, Mg-, K-, Ca- and NH₄-salts) for electrothermal vaporization coupled to inductively coupled plasma mass spectrometry (ETV-ICP-MS) for the determination of Mn, Cu, Zn, Cd and Pb has been studied. Solutions containing varying quantities (10–2000 ng absolute) of these salts have been added to four different amounts of analyte to study their suitability as modifier and their mass dependent influence. The best sensitivity enhancement for all elements tested was achieved with IrCl₃ and PdCl₂. From a comparison of the effect of PdCl₂ vs. Pd(NO₃)₂ it could be concluded that the mechanism of matrix modification also depends on the chemical form of the modifier. Particularly, for the volatile elements Cd and Zn differences in the behavior of the different chemical compounds of one metal (e.g. Pd) is evident, which shows that the enhancement effect is a result of the stabilization of the analytes in the graphite tube prior to vaporization and the improvement of the transport efficiency after vaporization.