Determination of Methotrexate at a Silver Solid Amalgam Electrode by Differential Pulse Voltammetry

Abstract

An ultrasensitive voltammetric method is reported for the determination of methotrexate using a polished modified silver solid amalgam electrode. Electrochemical behavior of this compound was examined using cyclic, linear sweep, and differential pulse voltammetry. Methotrexate provided two reduction and one oxidation signal in acidic and neutral media. The first reduction peak (E-p=-350 millivolts vs. Ag|AgCl electrode) and supporting electrolyte of pH 5 was chosen for further experiments. Differential pulse voltammetry parameters were optimized in combination with adsorptive stripping and the applicability of the method was verified. A low limit of detection (1.5x10(-10)moles per liter), good repeatability of determination (relative standard deviation<3.5%, n=5), and good repeatability of measurements (relative standard deviation of 1.7% at 1.0x10(-7)mole per liter methotrexate and n=11) was obtained. The method was employed for the accurate determination of methotrexate in a chemotherapeutic preparation.