Determination of Trace Cobalt in Water by Reversed Flow Injection Spectrophotometry

A method for determination of cobalt in water by flow injection spectrophotometry based on the catalytic effects of cobalt on the oxidation reaction of arsenazo III by potassium bichromate in HAc-NaAc buffer solution of pH 4.6 was established. The relationship of the reduced absorbency to the concentration of cobalt was good linearity and the maximum absorption peak located at 550 nm. The affecting factors on the strength of absorption including acidity, dosage, temperature, coexisting ions and so on, and the optimal conditions of the reaction in the system were investigated. Calibration graphs were linear for ranges of 0 to 20 μg/mL and a detection limit of 0.3 μg/mL cobalt was achieved. The proposed method was successfully applied to the analyses of industrial waste water samples, with relative standard deviation of less than 1.5% and the recoveries are 95.1% to 96.8%for the determination of cobalt.