Recent developments in automated determinations of trace level concentrations of elements and on-line fractionations schemes exploiting the micro-sequential injection - lab-on-valve approach

The determination of trace level concentrations of elements, such as metal species, in complex matrices by atomic absorption or emission spectrometric methods often require appropriate pretreatments comprising separation of the analyte from interfering constituents and analyte preconcentration. In this context sequential injection (SI) and lab-on-valve (LOV) schemes have proven themselves as superb vehicles to act as front-end microanalytical methodologies, particularly when employing solid-phase extraction (SPE) procedures. In this communication, selected SPE-procedures in a bead-renewable fashion are presented as based on the exploitation of micro-sequential injection (μSI-LOV) using hydrophobic as well as hydrophilic bead materials. The examples given comprise the presentation of a universal approach for SPE-assays, front-end speciation of Cr(III) and Cr(VI) in a fully automated and enclosed set-up, and the combination of SPE with fractionation schemes of environmentally interesting solid samples (such as soils or sediments) in order to conduct ecotoxicological studies.