Spectrophotometric determination of cobalt(II) in vitamin preparations, alloys and ores using phenanthraquinone monothiosemicarbazone

Abstract

Phenanthraquinone monothiosemicarbazone forms a brown 1 : 3 (metal : ligand) complex with cobalt(II). The complex is soluble in a water-methanol medium. The reagent has been used for the spectrophotometric determination of cobalt(II). The cobalt(II) complex has a maximum absorption at 500 nm with a sensitivity of 0.0048 µg cm^–2 for log l₀/l= 0.001. The optimum concentration range for the determination of Co^II is 0.8–4.0 p.p.m. over the pH range 6.8–8.5. The method has been used for the determination of cobalt(II) in a vitamin preparation, an alloy and an ore.