SPECTROPHOTOMETRIC DETERMINATION OF COBALT(III) WITH 1-(2-PYRIDYLAZO)-2-NAPHTHOL AND CETYLTRIMETHYLAMMONIUM BROMIDE

The developed spectrophotometric method of determination of cobalt(III) is based on the fact that cationic surfactant - cetyltrimethylammonium bromide (CTA) solubilizes Co(III)-PAN complex which is insoluble in water. In the presence of CTA the molar ratio of cobalt to PAN is 1:2. The optimum conditions for determination of cobalt were found. The application of buffer solutions was studied. Beer's law is obeyed over the range 0.1-1.0 mug ml-1 of cobalt, epsilon = 2.17 x 10(4) 1 mol-1 cm-1 at 570 nm. The main advantages of this method are as follows: reletively high sensitivity, simple and time-saving procedure, good accuracy and precision and wide pH range for complex formation. The method was used to determine cobalt in vitamin B12.