Analysis of cobalt chelate solution with chrome azophenol KS and determination of trace amounts of cobalt in metal samples

Abstract

Trace amounts of cobalt have been determined selectively by β-correction spectrophotometry with chrome azophenol KS (CAKS) at <em>p</em>H 8.5. The Co(II)-CAKS reaction is very selective in the presence of EDT A. The characteristic factors of the chelate formed can be computed more accurately because of the elimination of the interference of the excess CAKS by the updated method of β-correction spectrophotometry. Results show that Co/CAKS = 1.2 in the chelate, its practical molar absorptivity is equal to 2.10 x 10⁴ L.moI^-1 cm^-1 at 590 nm and its instability constant is 5.97 x 10^-13. The method has been applied for analysis of metal samples and the results show that the detection limit of cobalt is 0.01 mg/L and the recovery of cobalt between 93.0 and 106% with the RSDs of less than 4.3%.