الفهرس 
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Abstract
Two simple, highly sensitive and selective catalytic methods are described for the determination of Cr(VI) in natural and highly polluted wastewaters. The methods are based on the H2O2 oxidation of 2-aminophenol (AP) and o-dianisidine (3,3´-dimethoxybenzidine, DA). In the first method, the fixed time kinetic measurement is applied by tracing the oxidation product, both spectrophotometrically at 435 nm and by a digital camera, after 10 min of mixing the reactants. The optimum reaction conditions were: 5 mmol L-1AP, 0.2 mol L-1 H2O2, 0.09 mol L-1 borax, 1.0 v/v% Tween 60 and 0.5 mmol L-1 phosphoric acid (pH=6.45±0.05) at 45C. The calibration graph was linear up to 12.0 ng mL-1 of Cr(VI) and the detection limit (3Sb) was 0.16 ng mL-1. However, in the second method, the initial rate kinetic measurement was adopted by tracing the oxidation product, both spectrophotometrically at 440 nm and by a digital camera, for 2 min. of mixing the reactants. The optimum reaction conditions were: 5 mmol L-1 DA, 0.6 mol L-1 H2O2, 2.0 v/v% Tween 20 and 0.01 mol L-1 chloroacetate buffer (pH 4.5±0.05), at 30C. The linear range of the calibration graph
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was up to 90.0 ng mL-1 of Cr(VI) with a detection limit (3Sb) of 1.29 ng mL-1. The implemented methods were conveniently applied to the assessment of hexavalent chromium in natural and highly polluted industrial waste water. The analytical data were statistically in excellent agreement with those obtained following the standard ETAAS method. A comparison of published catalytic-spectrophotometric methods is also presented.
Key words: Digital Camera, Catalytic determination of Cr(VI), Natural and industrial wastewater, 2-aminophenol, O-dianisidine.