A sensitive and simple extractive-spectrophotometric method for the determination of microgram amount of cobalt by using alpha-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 r ange of 8.8-9.3 to form a yellow-color chelate, which is extracted in chlor oform, 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 co ncentration range of 0.08 - 2.2 mug/ml cobalt. The molar absorptivity of th e extracted species was 2.55 x 10(4) dm(3)/mol cm at 380 nm, with a detecti on limit of 0.01 mug/ml cobalt. Relative standard deviations of 0.4, 0.8 an d 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 determin ation 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 met hod is sensitive, simple, rapid and accurate.