CATALYTIC SPECTROPHOTOMETRIC DETERMINATION OF COBALT(II) BY SULFANILIC ACID - HYDROGEN PEROXIDE SYSTEM

A kinetic spectrophotometric method for the determination of trace Co(II) is developed. It is based on the catalytic effect of Co(II) on the oxidation of SA by hydrogen peroxide in alkaline media. The reaction was monitored spectrophotometrically by measuring the increase in absorbance of the reaction product at 370 nm. A fixed-time method of 15 min from the initiation of the reaction was used. The parameters affecting the sensitivity were optimized. The proposed catalytic method permits determination of Co(II) over the range 6 – 60 ng mL -1 with detection limit of 1.77 ng mL -1 . The relative standard deviations (n=10) are 2.8 % and 4.2 % for 6 and 60 ng mL -1 Со(ІІ), respectively. The method was applied successfully to the determination of cobalt in synthetic samples.