HPLC-AAS Interfaces for the Determination of Ionic Alkyllead, Alkyltin, Arsonium and Selenonium Compounds

Abstract

It has been estimated (Randall, 1984) that only 10 to 15 percent of the known compounds are sufficiently volatile and thermally stable to survive a gas chromatographic separation intact. A variety of ingenious derivatization procedures were devised to improve the gas chromatographic behaviour of thermally labile and/or non-volatile analytes. For example, cationic alkyllead species [R₃PbX, R₂PbX₂; R = CH₃, C₂H₅; X = anion] were ethylated, propylated, butylated, phenylated, or converted to their corresponding hydrides either prior to or in conjunction with gas chromatography-atomic absorption spectrometry (GC-AAS) (Van Cleuvenbergen et al., this volume). In our hands the butylation of alkylleads, when present at μg/kg concentrations in fatty tissues, proved to be technically demanding, labour- intensive, and time-consuming. Moreover, under certain conditions, transalkylation (redistribution) reactions were observed as an artefact of the derivatization procedure (Blais and Marshall, 1986). These problems prompted us to investigate the coupling of other chromatographic techniques with quartz tube (QT)-AAS for the determination of selected ionic organometallic species. Relative to GC, high performance liquid chromatography (HPLC) has a lower resolving power which can be improved somewhat (microbore techniques) at the expense of sample capacity. For liquid samples the major limiting factor for virtually all atomic spectroscopic techniques is the process of sample introduction. The conversion of liquid sample to atomic vapour is a notoriously inefficient process (Browner and Boorn, 1984a, b). The direct coupling of HPLC with a spectroscopic detector requires that the column eluate be introduced in a continuous and pulseless mode.

¹On leave from