Determination of 6-mercaptopurine in the presence of uric acid using modified multiwall carbon nanotubes-TiO2 as a voltammetric sensor.

In this work, a multiwall carbon nanotubes modified electrode (prepared by incorporating TiO(2) nanoparticles with p-aminophenol as a mediator) was used as voltammetric sensor for the determination of 6-mercaptopurine (6-MP) in the presence of uric acid (UA). The voltammograms of 6-MP and UA in a mixture can be separated from each other by differential pulse voltammetry with a potential difference of 380 mV at a scan rate of 10 mV s(-1). These conditions are sufficient to allow for the determination of 6-MP and UA both individually and simultaneously. The electrocatalytic currents increase linearly with 6-MP concentration in the ranges of 0.09-350 µmol L(-1) (two linear segments with different slopes). The detection limit for 6-MP was 0.065 µmol L(-1) . The RSD% for 1.0 and 15.0 µmol L(-1) 6-MP were 0.7%, and 1.2%, respectively. The kinetic parameters of the system were determined using electrochemical approaches. The method was successfully applied for the determination of 6-MP in drug sample, and 6-MP plus UA in urine samples.