The extraction-photometric determination of cadmium and cobalt with 4-(2-thiazolylazo)-resorcinol and 1-(2-thiazolylazo)-naphthol

Abstract

An efficient extraction of charged cobalt and cadmium complexes is possible with the addition of suitable organic bases, which permit the formation of neutral ion-association complexes of the nature (2B +-Me(II)-A 2 2−). After extraction, cobalt or cadmium can be determined by atomic absorption spectroscopy. Cadmium can be determined down to 0.06 p.p.m. in an isoamyl alcohol solution sprayed directly into an air-acetylene flame. The determination of cobalt is slightly less sensitive. A specific spectrophotometric method is also proposed for cobalt, based on the fact that the cobalt chelate cannot be re-extracted into the water phase in the presence of EDTA. Beer's Law is observed for 0.05–2 p.p.m. of cobalt; the molar absorptivities for the TAR and TAN complexes of cobalt in benzene are 2.5·10 4 and 3.7·10 4, respectively, at 570 nm.