Determination of chromium(III) and chromium(VI) in river water by electrothermal atomic absorption spectrometry after sorption preconcentration in a microwave field

Abstract

A rapid and sensitive method for the differential determination of Cr^III and Cr^VI in river water is described. Chromium species can be separated by sorption on a polymeric Detata sorbent containing conformationally flexible aminocarboxylic groups. Preconcentration using either static or dynamic conditions is possible. Microwave heating energy was used to promote the sorption. Quantitative sorption of Cr^III was achieved at pH 7, and that of Cr^VI at pH 3; hence, complete isolation of the two forms of Cr is possible. The optimum conditions (flow rate and sorbent volume) for sorbent extraction of Cr^III and Cr^VI were evaluated. The technique developed is based on the ability of the sorbent to preconcentrate Cr rapidly under dynamic conditions in the presence of a microwave field. Determination of Cr by electrothermal atomic absorption spectrometry is possible either after desorption or directly in the sorbent phase. The detection limit (based on the 3s criterion) is 30 ng l^–1; the technique is characterized by high reproducibility.