The ETV as a thermochemical reactor for ICP-MS sample introduction

Electrothermal vaporization (Em) for sample introduction into (inductively coupled) plasmas has been explored for more than two decades, first for use with optical spectroscopy and subsequently with mass spectrometry. It is with the latter that its full potential has been appreciated vis-a-vis solution sample nebulization. Tandem coupling of an ETV to a plasma source elicits a number of attractive features, not least of which is the explicit use of the device as a thermochemical reactor for in situ pretreatment of samples. This aspect of ETV use has not yet been sufficiently well explored, despite an accumulated body of literature in the related field of ETAAS, where judicious selection of thermal programs and chemical modifiers has been extensively used to minimize analytical problems. Of particular interest for ETV sample introduction is the feasibility of using classical chemical modifiers or other reagents to alter the volatility of either the analyte or the concomitant matrix, thereby permitting a thermal or temporal separation of their release from the ETV surface. This approach may alleviate space charge interference effects, minimize polyatomic ion interferences and effectively enhance resolution, permit direct speciation of trace element fractions in samples as well as serve as a 'crucible' for sample preparation. The literature in this field is reviewed and examples of such applications for ICP-AES and ICP-MS detection are presented.