Spectrophotometric determination of cobalt by extraction of benzyltributylammonium tetrathiocyanatocobaltate(II)

Cobalt (0–120 μg) can be determined spectrophotometrically at 625 nm after its extraction as benzyltributylammonium tetrathiocyanatocobaltate(II) into chloroform at pH 7. The effects of pH, diverse ions and masking studies are reported. The method has been applied to the determination of cobalt (0.2–10.0%, w/w) in high speed tool steels without prior separation of iron, and in vitamin B12.