Mechanisms of the action of platinum metal modifiers in electrothermal atomic absorption spectrometry: aims and existing approaches

The characteristics of As, Se and In in pure solutions in the presence of pre-reduced Pd, Rh, Ru, Pt and Ir modifiers in the transverse heated graphite atomizer (THGA) for electrothermal atomic absorption spectrometry are studied. Main attention is given to the influence of a wide range of modifier masses to sensitivity and shape of the absorption signals. Over-stabilization of As and In was observed in the presence of moderate amounts of the Pt modifier. Over-stabilization of As begins in the presence of approximately 2 μg of Rh and the addition of 25 μg of this modifier result in almost 3-fold suppression in the integrated absorbance. More than 2-fold suppression was also observed for the In absorption signals in the presence of 25 μg of Ru modifier. Modern knowledge of mechanisms on the action of platinum metal modifiers can neither predict, nor explain these element-specific interactions. Clear correlation between physical properties of the modifiers and analytes, and the data obtained could not be recognized as well. This significant contribution to chemical processes to stabilization of analytes during pyrolysis stage and their subsequent atomization. Some modern approaches concerning mechanisms of the action of platinum group metal modifiers are critically discussed and some trends are underlined.