2-ヒドロキシ-1-ナフトアルドキシムを用いるコバルト(II)の抽出吸光光度定量

抄録

An extraction-spectrophotometric method for the determination of cobalt(II) using 2-hydroxy-1-naphthaldoxime(HNA) was studied. Cobalt(II) reacts with HNA to form a water insoluble complex in aqueous solution in the pH range of 8.39.2, which can be extracted quantitatively into ethylacetate and has an absorption maximum at 387 nm. The cobalt complex in ethylacetate was stable and showed molar absorption coefficient of 1.17 × 10⁴ dm³ mol^-1 cm^-1. Under the optimum conditions, the colored system obeyed Beer's law over the range of 050 μg of cobalt (II) in 10 ml of ethylacetate. The sensitivity was 5.1 × 10^-3 μg Co(II)/cm² for 0.001 absorbance, and the coefficient of variation was 0.93% in six determinations. The recommended procedure is as follows : take an aliquot of sample solution containing up to 50 μg of cobalt(II) to a 50 ml separatory funnel. Add 10 ml of borax buffer solution (pH 8.8), and dilute with water to about 30 ml. Then add 10 ml of 0.01 M HNA ethylacetate solution and shake vigorously for 10 min. Filter the organic phase through a dry filter paper and measure the absorbance at 387 nm against reagent blank. Copper (II), iron(III), and nickel(II) seriously interfere with the determination of cobalt(II).