Extraction and spectrophotometric determination of cobalt(II) with thiobenzoylacetone and simultaneous determination of cobalt and nickel

Thiobenzoylacetone in benzene is used for the extraction and spectrophotometric determination of cobalt at pH 8.4-9.1. The orange-yellow complex is measured at 460 nm. The system conforms to Beer's law over the range 0.20-4.58 microg ml of extract. The colour of the complex is stable for at least 144 hr. Cobalt(II) is quantitatively extracted and determined in the presence of 200:1 (w w ratios) of various ions. The method is made selective by using common sequestering agents such as thiourea or fluoride or by selective extraction with mesityl oxide, tributylphosphate and acetylacetone. It is possible to determine cobalt in the presence of nickel by simultaneous spectrophotometry. The method is rapid, simple, selective and sensitive.