Abstract：A sensitive catalytic spectrophotometric method for determining μg·L-1 of chromium(Ⅵ) has been developed. The method, based on the catalytic effect of Cr(Ⅵ)on the oxidation of aligarin red with hydrogen peroxide, was monitored spctrophotometrically in the medium of microemulsion which consists of CTMAB , n-pentanol, n-heptane and water. The variables affecting the rate of the reaction were investigated. The linearity range of the calibration graph is dependent on the reaction temperature. The sensitivity of this method is 72.5% higher in the microemulsion medium than in CTMAB medium. The apparent active energy of the catalytic reaction is 55.7 kJ·mol-1. The calibration graph is linear for 2.4-75 μg·L-1 Cr(Ⅵ)at 80 ℃, the detection limit is 4.27×10-10 g·mL-1, and the relative standard deviation of eleven determinations of 60 μg·L-1 Cr(Ⅵ)was 1.84%. The method has been successfully applied to the determination of chromium(Ⅵ)in the electroplating waste water.
Key words：Microemulsion;Catalytic spectrophotometry;Chromium(Ⅵ);Aligarin red
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