Analytical Sciences

A Sensitive and Simple Extractive-Spectrophotometric Method for the Determination of Microgram Amount of Cobalt by Using alpha-Benzilmonoxime

Habibollah ESKANDARI, Hassan S. GHAZIASKAR,  and Ali Asghar ENSAFI

College of Chemistry, Isfahan University of Technology, Isfahan 84154, Iran

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. Under 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 ug/ml cobalt. The molar absorptivity of the extracted species was 2.55x10⁴ dm³/mol cm at 380 nm, with a detection limit of 0.01 ug/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 ug/ml, respectively. The effect of diverse ions on the determination of 1.00 ug/ml of cobalt has been studied. The method was applied to the determination of cobalt in vitamin B12 and B-complex ampoules, a Co₂O₃-Co₃O₄ laboratory chemical mixture and some synthetic alloy samples. The method is sensitive, simple, rapid and accurate.

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