Electrochemical study of the antiplatelet agent clopidogrel and its determination using differential pulse voltammetry in bulk form and pharmaceutical preparations with a glassy carbon electrode.

In the present study, the electroanalytical behaviour of clopidogrel (CLP) bisulfate, an antithrombotic drug, was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques using a glassy carbon electrode (GCE). The anodic oxidation of clopidogrel bisulfate was investigated with a GCE to determine the oxidation conditions. The voltammograms of solutions having various concentrations of clopidogrel were recorded in order to obtain the optimum oxidation conditions of this drug on a GCE. To determine the effects of the nature of the supporting electrolyte, pH and scan rate on the anodic oxidation reactions, the experiments were performed in 0.2 M sulphuric acid, and in Britton-Robinson (BR) (pH 2-5) and acetate (pH 3.5-5.63) buffers with a 10-400 mVs(-1) scan rate interval. The oxidation of clopidogrel bisulfate was found to be diffusion-controlled over a concentration range of 0.08 mM-1.0 mM in pH 3.7 acetate buffer by an optimized DPV technique. The voltammetric method developed was applied to the tablet form of pharmaceutical preparation of this compound and the accuracy, precision, selectivity, sensitivity, repeatibility within and between days and reproducibility of the proposed method was investigated statistically. The results were compared with the spectrophotometric and HPLC methods developed in our laboratory and found to be in good agreement. No interference was observed from common pharmaceutical adjuvants.

Electrochemical behaviour of sertraline hydrochloride at a glassy carbon electrode and its determination in pharmaceutical products using osteryoung square wave voltammetry.

In this study the electrooxidation of sertraline (STR) hydrochloride in pH 8 Britton-Robinson buffer (BRb) -methanol (MeOH) (1:1,v/v) supporting electrolyte was investigated using Osteryoung Square Wave Voltammetry (OSWV) with the glassy carbon electrode. OSWV is a rapid and sensitive electro-analytical technique for sertraline determination. This study indicated that sertraline was susceptible to oxidation. The effects of the supporting electrolyte, pH and scan rate on the anodic reactions performed in BRb and a scan rate interval 5 - 1000 mVs(-1) were investigated. Sertraline hydrochloride was oxidized irreversibly and diffusion controlled. OSWV was selected for the quantitative determination. Using optimized OSWV technique, the current was linear within a concentration range of 0.04-0.8 mM in pH 8 BRb which at the equivalent volume with MeOH. The applicability of the proposed method was shown by the successful analysis of sertraline in tablet dosage forms. Accuracy, precision, selectivity, sensitivity, within day and between days reproducibility of the method were investigated statistically. Application of the suggested method to pharmaceutical formulation is presented and compared with the UV spectrophotometric and HPLC methods. The results were found to be in a good agreement. No interference was observed from common pharmaceutical adjuvants.

Simultaneous determination of pseudoephedrine sulfate, dexbrompheniramine maleate and loratadine in pharmaceutical preparations using derivative spectrophotometry and ratio spectra derivative spectrophotometry.

Two new spectrophotometric methods are described for the simultaneous analysis of pseudoephedrine sulfate-dexbrompheniramine maleate (DBP) and pseudoephedrine sulfate-loratadine combinations. In the first, derivative spectrophotometry, dA/dlambda values were read at zero-crossing points. In the second, ratio spectra derivative spectrophotometry, analytical signals were measured at the wavelengths corresponding to either maxima or minima for these drugs in the first derivative spectra of their ratio spectra. The procedures do not require any separation step. Mean recoveries were found to be >99% in the methods for these compounds in their synthetic mixtures. All the spectrophotometric methods proposed were compared with each other and HPLC which was also developed by us and applied to the pharmaceutical preparations selected.

Voltammetric determination of chlorpromazine hydrochloride.

The electrochemical behaviour of chlorpromazine hydrochloride (CPZ-HCI) in sulphuric acid was investigated voltammetrically using ruthenium electrodes and it was subsequently determined by the same method. From the recorded voltammograms it was concluded that CPZ-HCI can be determined in the concentration range 2 x 10(-4)-8 x 10(-4) M (71-284. 3 micrograms ml-1). The proposed voltammetric method was applied to the determination of CPZ-HCI in tablets used for neuroleptic purposes in Turkey; the amount of effective compound was found to be within the ranges given for a pharmacopoeial procedure.

Electrochemical analysis of some phenothiazine derivatives--I. Chlorpromazine HCl.

In this study the electrochemical behaviour of chlorpromazine hydrochloride in sulphuric acid solutions has been examined by cyclic and linear sweep voltammetry using oxidised and non-oxidised ruthenium wire electrodes. Although a stable and permanent RuO(2) coating on the electrode took a long time to prepare, the resulting curves were highly reproducible. It was possible to study solutions in a wide concentration range only by use of scan rates lower than 20 mVs(-1). The cyclic voltammograms of chlorpromazine hydrochloride in solutions of different concentrations of sulphuric acid and the behaviour of oxidised and non-oxidised ruthenium electrodes have been compared.