Determination of chromium(III) and total chromium in water by derivative atomic absorption spectrometry using flow injection on-line preconcentration with a double microcolumn

A rapid and sensitive method has been proposed for the sequential determination of chromium(III) and total chromium in water samples by flame atomic absorption spectrometry combined with a flow injection on-line preconcentration on a double-microcolumn. The chromium(III) and total chromium in samples were retained on a double-microcolumn with a cation exchange resin, respectively, and eluted directly into a nebulizer by 3 mol L-1 HNO3. The characteristic concentration (gives a derivative absorbance of 0.0044) and the detection limit (3sigma) for chromium were 0.512 mug L-1 and 0.647 mug L-1 for a preconcentration time of 1 min, respectively. This is an improvement of 20 and 14-times than those of conventional FI-FAAS. The proposed method allows the determination of chromium in the range of 0-90 mug L-1 with a relative standard deviation of 3.63% at the 10 mug L-1 level. The method has been applied for the analysis of chromium in reference water of National Research Center for Certified Reference Materials (GBW08607) and other water samples with satisfactory results.