Cerium-doped flower-shaped ZnO nano-crystallites as a sensing component for simultaneous electrochemical determination of epirubicin and methotrexate

A glassy carbon electrode (GCE) was modified with cerium-doped ZnO nanoflowers (Ce-ZnO/GCE) to obtain a sensor for direct simultaneous detection of the cancer drugs epirubicin and methotrexate. XRD, SEM and EDX techniques were used to characterize their morphology and structure. Electrochemical impedance spectroscopy was applied to characterize the electrochemical features of the modified GCE. The experimental conditions were optimized. Diffusion coefficients and heterogeneous rate constants were determined for the oxidation of epirubicin. The differential pulse voltammetric response to epirubicin has a peak near 0.7 V (vs. Ag/AgCl at a scan rate of 50 mV s(-1)) and is linear in the 0.01 to 600 mu M concentration range, and the detection limit is 2.3 nM (S/N = 5). The differential pulse voltammetric response to methotrexate has a peak near 0.75 V (vs. Ag/AgCl and the same scan rate) and is linear in the 0.01 to 500 mu M concentration range, and the detection limit is 6.3 nM (S/N = 5). The method was applied to the simultaneous determination of epirubicin and methotrexate in pharmaceutical injections and in spiked diluted blood specimens.