KINETIC SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF URINARY COBALT-BASED ON ITS CATALYTIC EFFECT ON THE OXIDATION OF L-ADRENALINE HYDROCHLORIDE BY HYDROGEN-PEROXIDE

A catalytic reaction for determination of nanomolar concentrations of Co(II), i.e., oxidation of L-adrenaline hydrochloride with H2O2 in alkaline medium, is proposed. The reaction gives a low limit of detection of 2.5 x 10(-9) M Co(II) in the reaction mixture, good reproducibility with a relative standard deviation (R.S.D.) of 4-5% in the Co(II) concentration range 8.0 X 10(-9) -8.0 X 10(-8) M and good selectivity. On the basis of this indicator reaction, a catalytic-spectrophotometric method for the determination of cobalt in small urine samples (5.00 mi) was elaborated. The analysis of 17 urine samples, taken from healthy persons of different ages, gave cobalt concentrations in the range 0.20-1.50 mu mol l(-1). The R.S.D. for ten replicate analyses of a urine sample with an average cobalt content of 0.63 mu mol l(-1) was 5.6%. The reliability of the method was verified by a comparative phorometric method (r = 0.9755) and by a determination based on known additions of cobalt (r = 0.9894).