Selective determination of cobalt using polyurethane foam and 2-(2-benzothiazolylazo)-2-p-cresol as a spectrophotometric reagent

The present work describes a selective, rapid and economical method for the determination of cobalt using the 2-(2-benzothiazolylazo)-p-cresol (BTAC) as a spectrophotometric reagent associated with a solid extraction on polyurethane foam. The BTAC reacts with Co(II) in the presence of Triton-X100 surfactant forming a green complex with maximum absorption at 61.5 nm. The reaction is used for cobalt determination within a pH range of 6.50-7.50, with an apparent molar absorptivity of 1.62 x lo4 L mol- ’ cm- ‘_ Beer’s Law is obeyed for a concentration of at least 1.60 ug ml-1. A selective procedure is proposed for cobalt determination in the presence of Fe(II), Hg(II), Zn(I1) and Cu(I1) up to milligram levels using masking agents. Polyurethane foam is used for the preconcentration and separation of cobalt from thiocyanate media and this procedure is applied to its determination in nickel salts and steel alloys