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

The microwave sorption preconcentration of chromium under dynamic conditions is described followed by determination of chromium in the eluate, or in the solid phase of the sorbent, by ETAAS. Chromium species present in river water were separated by sorption on a polymeric Detata sorbent containing conformationally flexible aminocarboxylic groups. Microwave heating energy was used to promote the sorption. Quantitative sorption of chromium(III) was achieved at pH 7, and that of chromium(VI) at pH 3. Thus, complete isolation of the 2 species of chromium was possible. Optimal conditions of flow rate and sorbent volume were evaluated. The detection limit for both chromium species was 30 ng per litre and method reproducibility was good.