Simultaneous determination of melatonin and pyridoxine in tablet formulations by differential pulse voltammetry

A method has been developed for the simultaneous determination of melatonin (MT) and pyridoxine hydrochloride (PY) in pharmaceutical dosage forms by differential pulse voltammetry, based on the oxidation of both drugs at a glassy carbon electrode. Cyclic and linear scan voltammetry were used to examine the influence of pH, nature of the buffer, scan rate and concentration. The results in 0.5 M H2SO4 with 20% methanol allowed a method to be developed for the determination of MT and PY simultaneously and in the presence of each other in the ranges 2 x 10(-5)-8 x 10(-5) and 2 x 10(-5)-4 x 10(-4) M, with the detection limits of 5.86 x 10(-6) and 2.45 x 10(-6) M, respectively. The proposed method was successfully applied to the commercial tablets containing this drug combination without any interference by the excipients.