Spectrophotometric determination of cobalt(II) using cetyltrimethylammonium bromide and thiocyanate

Abstract

Cobalt(II) forms a bluish 1:2:1 complex with thiocyanate and cetyltrimethylammonium bromide at room temperature in a hydrochloric acid medium. The complex, extractable by chloroform, has ?max at 625 nm. Beer's law is obeyed for 0.05-8.0 ?g mL-1 of cobalt. The Sandell sensitively of the reaction is 0.008 ?g cm-2 and the molar absorptivity is 2.21 × 104 L mol-1 cm-1. The tolerance limits to base metals and common anions are reported. The simple and rapid method is successfully applied to the determination of cobalt in a vitamin B12 preparation and in synthetic alloys containing nickel, iron and chromium.