Investigations Into the Role of Modifiers for Entrapment of Hydrides in Flow Injection Hydride Generation Electrothermal Atomic Absorption Spectrometry as Exemplified by the Determination of Germanium

Abstract

Pd-conditioned graphite tubes, placed in the furnace of an AAS instrument, were used for entrapment of germane as generated in an associated flow-injection system. Two different approaches were tested with the ultimate aim of allowing multiple determinations, i.e. , introduction of the modifier as a Pd salt solution, and use of electrolytically Pd pre-coated tubes. While the former treatment resulted in satisfactory analytical performance, although requiring separate regeneration of the tubes prior to each sampling sequence, the electrolytically pre-coated tubes did not function satisfactorily. This in turn led to a closer investigation as to the function of Pd in entrapping hydrides and releasing the analyte. Based on an evaluation of the behaviour of the two types of tubes, supplemented by scanning tunnelling microscopy studies of tubes with and without modifier and treated in different ways, it is shown that heating at 2600 °C results in a physical–chemical change of the modifier in the electrolytically coated tubes; however, this change leads only to a loss of the ability of the modifier to entrap the hydrides, while the stabilizing effect is maintained.