Recent advances in adsorptive stripping voltammetry (AdSV) are reviewed. The mechanisms of the adsorptive and stripping steps are given. The criteria of ligand selection, along with the present status and future trends in AdSV for trace element analysis, are discussed. Tables containing the elements determined by AdSV and the ligands used in AdSV, as well as the real samples analyzed and operational conditions, are presented (together with 171 references).
Abstract.A sensitive voltammetric method is presented for the determination of trace amounts of total chromium (Cr(III) and Cr(VI)) in natural waters, employing the square wave mode. The method is based on the preconcentration of the Cr(III)-TTHA complex by adsorption at the HMDE at the potential of -1.0 V vs. Ag/AgC1. The adsorbed complex is then reduced producing a response with a peak potential of -1.29 V and the peak height of the Cr(III) reduction is measured. The catalytic action of the nitrate ions on the Cr(III)-TTHA reduction has been elucidated using cyclic voltammetry. The adsorption of chromium complexes at the HMDE was investigated using out-of-phase a.c. voltammetry and the potential range of adsorption was determined.Based on these investigations optimal conditions for the determination of the total chromium concentration in the range 155-2000 ng 1-1 have been established. The determination limit is 15 ng 1-1 and the RSD is 3.5% for chromium concentrations > 200 ng 1-1.The usefulness and wide scope of this method for reliable and highly sensitive chromium analysis down to the ultra trace levels existing in various types of natural waters is demonstrated by determinations of the total chromium content in lake, sea and rain water.Key words: chromium, square wave voltammetry, adsorptive voltammetry, triethylenetetranitrilohexaacetic acid.Chromium is a very important ecotoxic trace metal in the aquatic environment and a sufficiently sensitive analytical method for the reliable determination of chromium in natural waters would be of great interest. The relatively inert chromium (III) species and the reactive more toxic chromium (VI) species [1][2][3] are present in natural waters in various concentrations, from 0.1 to 0.5/~g 1-1 in ocean waters [4] and 200 gg 1-1 in some polluted ground waters [5]. Most of the soluble chromium
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