CHROMIUM SPECIATION BY A SURFACTANT-COATED ALUMINA MICROCOLUMN USING ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A simple and convenient method has been developed for the speciation of chromium(III) and chromium(VI) in aqueous solutions using a sodium dodecyl sulphate coated alumina micro-column (1.5 cm x 5 mm i.d.) and graphite furnace-atomic absorption spectrometry (GF-AAS). Under the optimized conditions (pH 0.6, adjusted with hydrochloric acid; flow rate, 1 ml min(-1)) chromium(VI) is retained on the column and chromium(III) is collected and determined by GF-AAS. Total chromium is directly determined by GF-AAS and chromium(VI) is calculated by difference. The relative standard deviations (10 replicate analyses) at the 20 mu g l(-1) level for chromium(III) and chromium(VI) and at the 40 mu g l(-1) level for total chromium were 1.4%, 3.6% and 1.8%, and the corresponding limits of detection (based on 3 sigma) were 0.57 mu g ml(-1), 0.61 mu g ml(-1) and 0.35 mu g l(-1) respectively. No large interference effects have been observed from other investigated species and the method has been successfully applied to a range of water samples.