Simultaneous determination of dissolved inorganic chromium species in wastewater/natural waters by surfactant sensitized catalytic kinetic spectrophotometry

AbstractA simple, rapid, highly accurate and sensitive kinetic method is proposed for determining chromium(VI). The method is based on its catalytic effect on the oxidation of Celestine blue (CB+) by H2O2 in the presence of 2,2′-bipyridyl (Bipyr) and cetylpyridinium chloride (CPC) at pH 6.50. The reaction was monitored spectrophotometrically by measuring the absorbance of indicator dye at 645nm. The analytical variables, which have influences on the sensitivity, were investigated and the optimum conditions were established. The optimized conditions made it possible to determine and speciate chromium in a linear range of 5–200μgL−1 with a detection limit of 0.65μgL−1. The recoveries and relative standard deviations (RSDs) for the determination of 10, 25, 75 and 150μgL−1 Cr(VI) (n: 5) were in the range of 99.0–99.8% and 0.2–3.5%, respectively. The selectivity was also studied and greatly enhanced by adding a suitable masking mixture. The method was successfully applied to the simultaneous analysis of Cr(III) and Cr(VI) in natural water and waste water samples with a recovery changing in the range of 95–103% for Cr(III) and 100–104% for Cr(VI). Its accuracy was validated by the analysis of certified reference materials with good agreement between certified and found values