Catalytic cathodic stripping voltammetry of 6-mercaptopurine-9-D-riboside in the presence of nickel ion

Differential pulse CSV of 6-mercaptopurine-9-D-riboside (6-MPR) on a HMDE was investigated at pH about 7 in the presence of nickel ion. According to the value of the accumulation potential, 6-MPR was preconcentrated either as a mercury compound or an adsorbed nickel complex. During the subsequent cathodic scan, 6-MPR does catalyze the reduction of nickel ion giving a peak at about -0.8 V (vs. SCE). This peak enables the determination of B-MPR at concentrations down to 1 nM with no substantial interference from the heavy metal ions, chloride, alkali metals, complexing agents and only moderate interference by thiols and surface-active compounds. The best sensitivity and reproducibility were achieved under the following conditions: pH 7.5 (phosphate-acetate buffer); Ni2+, 1 mM; E-acc = -0.3 V; t(acc) = 1 to 2 min; scan speed = 20 mV/min; pulse interval = 0.2 s.