Polarographic activity of the antitumor drug cis-dichlorodiammineplatinum (II). The effect of hydrolysis and trans-isomerization of the drug.

Electrochemical activities of cis-dichlorodiammineplatinum (II) (cis-DDP) and its trans isomer were studied by classical and differential pulse polarography (d.p.p.). It was shown that both isomers yielded a polarographic step or peak at about -1.6 V (vs. Ag/AgCl), which corresponded to electroreduction of the complex and to catalytic hydrogen evolution. This signal was easily measurable with the aid of d.p.p. and was suitable for investigation of the extent of hydrolysis and trans-isomerization of cis-DDP leading to the formation of toxic products. The detection limit for determination of cis-DDP and its trans isomer by d.p.p. was 1 X 10(-6) mol/l.