Determination of cobalt in blood using cathodic stripping voltammetry

Abstract

A method was developed to determine low levels of cobalt in whole blood, serum and plasma. Samples of blood (0.2 ml) were mineralized at 160 °C in the presence of concentrated nitric acid. Residual organic matter was destroyed by digestion using ultraviolet irradiation after dilution with water. The cobalt concentration was determined by catalytic cathodic stripping voltammetry (CSV) preceded by adsorptive collection of cobalt complexed with diphenylglyoxime (DPG). The optimized analytical conditions for the CSV analysis included a DPG concentration of 0.5 µmol l^–1, 0.05 mol l^–1 ammonium chloride buffer (pH 9.3), 0.15 mol l^–1 nitrite, a deposition potential of –0.75 V, an adsorption time of 30–120 s and a negative potential scan using the differential-pulse modulation. The limit of detection was 40 pg of cobalt in 0.2 ml of blood, which was limited by the blank level of cobalt in the reagents after purification.