Spectrophotometric determination of cobalt in copper alloy with picramazochrom

The coloring reaction between coloring reagent picramazochrom and cobalt was studied.In ammonium citrate-ammonia water solution at pH 10,cobalt could react with picramazochrom to form a green complex,which had maximum absorption wavelength at 650 nm.The apparent molar absorptivity was 2.62×104 L·mol-1·cm-1.Beer's law was obeyed for cobalt in the range of 0-2.0 mg/L.The interference of matrix in solution could be eliminated by adding zinc to replace copper.The proposed method had been applied to the determination of cobalt in copper alloy,and the results were consistent with those obtained by nitroso R salt spectrophotometry.The relative standard deviation(RSD,n=5) was less than 2%,and the recovery was close to 100%.