THE STUDY OF DIFFERENTIAL-PULSE ADSORPTIVE STRIPPING VOLTAMMETRY OF CO(II) 1-NITROSO-2-NAPHTHOL CHELATE/

Cobalt (II)/1-nitroso-2-naphthol chelate in citrate/ammonium citrate ( pH 8.6) buffer solution is studied by adsorptive stripping voltammetry on a static mercury drop electrode (SMDE). The adsorbed chelate yield s one distinct peak at -0.51 V, which can be utilized to quantify trac e cobalt. The interfacial and redox behavior are evaluated by cyclic v oltammetry and pulse polarography. The effect of accumulation potentia l, accumulation time, and concentration of ligand on the reduction pea k currents of the chelate have been discussed. Possible interference m etal ions are also investigated. The peak current is proportional to t he concentration of cobalt in the range of 10(-7) to 10(-9) M (correla tion coefficient 0.998). The relative standard deviation is -2.6% at t he concentration of Co(II) 2.2 x 10(-8) M (n = 7). The detection limit of Co(II) is as low as 0.05 ppb (2-minute accumulation).