Polarographic determination of 6-mercaptopurine-9-D-riboside

The direct-current polarographic studies revealed that in the presence of MPR (0.002 to 0.02 mM), at pH around 7 (phosphate -acetate buffer), a catalytic nickel pre-wave forms at around -0.78 V vs. SCE. The catalytic nickel reduction involves the Ni(II) - MPR complex (1:1). The wave-shape of this catalytic wave is distorted at higher MPR concentrations due to another signal that takes place at more negative potentials. This characteristic makes difficult the application of the catalytic signal for MPR determination. The shape of the differential pulse-polarographic peak makes this signal more suitable for analytical purposes. The peak current is proportional to MPR concentration in the concentration range of 0.1 to 4 µM and the detection limit is 29 mg/l.