Electrochemical applications and computational studies on ephedrine drug

Abstract

A novel, simple, sensitive and highly selective pseudo-carbon paste electrode modified with poly(acrylic) acid (PCPE-PAA) was described to be useful for the electrochemical determination of ephedrine substance. The PCPE-PAA electrode was characterized using scanning electron microscope (SEM) and cyclic voltammetry. Cyclic voltammogram for ephedrine shows only one anodic oxidation peak at 1.15 V (vs. SCE) using Britton–Robinson buffer (pH 9). Theoretical calculations were performed using PM3 method to be helpful in studying the electrochemical behavior of ephedrine. The highest occupied orbitals (HOMO) of ephedrine and the lowest unoccupied orbitals (LUMOs) of its oxidation product (methcathinone) are mainly localized in the side chain of benzene ring. The values of HOMOs, LUMOs and atomic charges clearly indicate that the oxidation process occurs on the hydroxyl group of ephedrine forming ketone group, supporting the proposed electrochemical mechanism. Square wave voltammetry was used for the direct electrochemical determination of ephedrine. Ephedrine gives a linear range from 6 × 10−5 to 1 × 10−3 M with a correlation coefficient of 0.998 and a relative standard deviation of 2.165 × 10−7. A lower detection limit of 3.5 × 10−7 M was obtained. The effect of some interferences such as ascorbic acid, uric acid, urea, glucose and glycine on the peak height of ephedrine was examined. The suggested method has been applied successfully for the direct electrochemical determination of ephedrine in urine and different pharmaceutical formulations.