| 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, E 1/2, the diffusion coefficient, D, the number of electrons transferred in the reaction, n, the electron transfer coefficient, alpha, and the heterogeneous rate constant, ks, 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, E 1/2 = 0.67V, D = 3.9 x 10-5 cm2/s, n = 1mole, alpha = 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. |
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