The Electrochemical Study Of Promethazine HCl In Aqueous Solution At Glassy Carbon Electrode

Abstract

The electrochemical oxidation of promethazine hydrochloride (PMT) was studied on glassy carbon electrode (GCE) whose surface area (6.0 x 10 3 cm2) was determined electrochemically. The reference electrode was a commercial calomel electrode and the counter electrode was a wound platinum wire. The electrochemical reaction was conducted at room temperature in a one-electrochemical cell using an electrochemical analyzer supplied by Cypress Systems. The important electrochemical parameters such as the redox potential, Eo, the half-wave potential, E1/2, the diffusion coefficient, D, the number of electrons transferred in the reaction, n, the electron transfer coefficient, &alpha, and the heterogeneous rate constant, k_s, were determined in a solution of 4.0 x 10-3 M. These parameters were used in formulating a plausible reaction mechanism of this compound in an aqueous solution. The effect of different surfactants on its stability was also studied. The results of the obtained data indicate that: 1) The electrochemical parameters obtained for this compound were: Eo = 0.60V, E1/2,/super> = 0.67V, D = 3.9 x 10-5 cm2/s, n = 1mole, á = 0.33, ks = 2.45 x 10-4; 2) The peak potential was observed at about 0.60 - 0.80 V and was linearly dependent on the concentration; 3) The observed current intensity which was determined as a function of the voltammetric scan rate, was seen to be linearly related to the square root of the scan rate; 4) The observed peak potential and the peak current were influenced by the pH of the solution; 5) The stability of PMT in different surfactant (cationic, anionic and non-ionic) shows a decrease when compared to the control solution over twenty days. During this period, it was observed that the anionic and the non-ionic surfactants were more effective stabilizers than the cationic surfactants.