Online Spectrophotometric Determination of Cr(III) and Cr(VI) in Tannery Wastewater by LPIC-FIA

A highly selective, low-cost and easily operated method has been developed for on-line separation and simultaneous determination of Cr(III) and Cr(VI) by using low pressure ion chromatography combined with flow injection spectrophotometric analysis(LPIC-FIA). Based on the selective adsorption of a low pressure ion chromatographic column (LPICC) on Cr(III), a new online separation system of Cr(III) and Cr(VI) was proposed. Thus, the separated Cr(VI) and Cr(III) are successively reacted with salicylfluorone (SAF) to form an amaranthine complex in the presence of cetyltrimethylammonium bromide (CTMAB), respectively. The complex gave maximum absorbance at 570nm. All the variables were studied in order to optimize the reaction conditions. The calibration graphs were linear in the range of 10-1000 mu g L-1 (Cr(III)) and 5-1000 mu g L-1 (Cr(VI)) with correlation coefficients of 0.9996 and 0.9993, respectively. The R.S.D. obtained for 200 mu g L-1 of Cr(III) and 100g L-1 of Cr(VI) was 2.36% (n=12) and 2.17%, respectively. The method was applied for the simultaneous determination of Cr(III) and Cr(VI) in tannery wastewater with satisfactory results and recoveries in the range of 95.8%-104.6% and 96.5%-104.6%, respectively.