Research Papers
On-site Catalytic Determination of Trace Chromium(VI) in Fresh Water Using o-Phenylenediamine–Hydrogen Peroxide Reaction
2012 Volume 61 Issue 2 Pages 103-108
Details
2012 Volume 61 Issue 2 Pages 103-108
A sensitive and selective method for determination of Cr(VI) has been developed using chromium-catalyzed oxidation of o-phenylenediamine with hydrogen peroxide. Under an optimized condition, the absorbance at 430 nm and at a fixed reaction time of 10 min was proportional to the concentration of Cr(VI) up to 1 mg L−1. A detection limit (DL) was 1 μg L−1. On-site determinations were carried out using a laboratory-made palm-top size colorimeter with a red-green-blue light emitting diode. Measurement of the absorbance for blue light was used for the determination up to 1 mg L−1 with a DL of 1 μg L−1. A kinetic study derived an on-site reaction time of τ = τoexp[b(1/T–1/To)], where the standard reaction time τo = 10 min, b = 7.65×103, a standard reaction temperature To = 298 K. By this equation, τ giving an absorbance value at τo and To can be calculated for any on-site temperature (T) between 20 and 40°C. On-site analyses within an error of 6% were carried out without control of reaction temperature and with a laboratory-prepared calibration curve at τo and To. The proposed method was successfully applied to natural and standard river-water samples and an industrial waste-water sample.
