Electrocatalytic determination of 6-tioguanine at a p-aminophenol modified carbon paste electrode

A p-aminophenol modified carbon paste electrode (p-APMCPE) was constructed for determination of an anticancer drug 6-thioguanine (6-TG). The cyclic voltammogram showed that the electrocatalytic oxidation of 6-TG at the surface of p-APMCPE occurs at a potential about 840 mV less positive than at an unmodified electrode. Square-wave voltammetry results presented that the electrocatalytic oxidation peak Currents of 6-TG in pH 9.0 had two linear dynamic ranges in the range of 0.2 to 8.0 and 8.0 to 350.0 mu M 6-TG with a detection limit of 0.08 mu M. The kinetic parameters such as electron transfer coefficient (alpha) and rate constant were determined for the chemical reaction between 6-TG and p-aminophenol. Finally, this method was evaluated for the determination of 6-TG in 6-thioguanine tablets and urine samples.