A sensitive and simple extractive-spectrophotometric method for the determination of microgram amount of cobalt by using α-benzilmonoxime

alpha -Benzilmonoxime has been used for the extraction and determination of cobalt at microgram amount. The reagent reacts with cobalt(II) in the pH range of 8.8-9.3 to form a yellow-color chelate, which is extracted in chloroform, toluene, and some other non-polar solvents. The chelate is stable in chloroform for about one day, tinder the optimum conditions of the alpha -benzilmonoxime concentration and pH of 9.0, Beer's law was obeyed in the concentration range of 0.08 - 2.2 mug/ml cobalt. The molar absorptivity of the extracted species was 2.55 x 10(4) dm(3)/mol cm at 380 nm, with a detection limit of 0.01 mug/ml cobalt. Relative standard deviations of 0.4, 0.8 and 2.3% were found for the determination of cobalt concentrations of 2.2, 1.1 and 0.08 mug/ml, respectively. The effect of diverse ions on the determination of 1.00 mug/ml of cobalt has been studied. The method was applied to the determination of cobalt in vitamin Bit and B-complex ampoules, a Co2O3-Co3O4 laboratory chemical mixture and some synthetic alloy samples. The method is sensitive, simple, rapid and accurate.