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Abstract

A rapid, simple, and sensitive spectrophotometric method for determining trace amounts of chromium was studied. The method is based on the interaction of chromium with indigo carmine dye in acidic medium, with oxalates acting as a catalyst. The resulting bleaching of the dye is directly proportional to chromium(VI) concentration, measured at 610 nm. A plot of absorbance vs. chromium(VI) concentration obeys Beer’s law over the range of 0.5-70 μg/25 mL (0.02-2.8 ppm), with a molar absorptivity of 1.71 × 10^4 L·mol^-1·cm^-1 and Sandell’s sensitivity index of 0.0030 μg·cm^-2. The detection limit is 0.0012 μg/mL, and the relative standard deviation ranges from ±0.70% to ±1.86%, depending on concentration. The method has been successfully applied to water samples, pharmaceutical preparations, and standard rock sample (MRG-1).

Keywords

Chromium, Indigo Carmine, Spectrophotometric

Article Type

Article

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