Voltammetric and HPLC techniques for the determination of paroxetine hydrochloride.

The antidepressant agent paroxetine hydrochloride (POT) was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and osteryoung square wave voltammetry (OSWV). A sensitive method is described for the determination of POT in its pure form and in human plasma. The linear relationship between concentration and peak current permits the quantification of POT by CV, DPV and OSWV in the concentration range of 2 x 10(-5) - 8 x 10(-4) M. Applicability to tablets and human plasma analysis has been illustrated. Furthermore, a HPLC method with diode array detection was developed. Linearity was established between 2 x 10(-7) - 6 x 10(-5) M for POT. The described methods were successfully employed with high degrees of precision and accuracy for the estimation of total drug content in human plasma and pharmaceutical dosage forms of POT.

High-performance liquid chromatographic analysis of verapamil and its application to determination in tablet dosage forms and to drug dissolution studies.

A high-performance liquid chromatographic procedure with two detectors is presented for the determination of verapamil in pharmaceutical dosage forms. The procedure is based on the use of reversed-phase high-performance liquid chromatography with UV and fluorimetric detectors. Each analysis required no longer than 6 min for both detection procedures. Quantification was achieved by measurement of the ratio of the peak area of the drug to the internal standard (fluoxetine) and the detection limit was 10 ng/ml for the UV detector and 750 pg/ml for the fluorimetric detector. There was no significant difference between inter- and intra-day studies for verapamil determined for two different concentrations (0.05 and 1.00 microgram/ml). This process could be used to determine verapamil concentrations in the range 0.025-50 and 0.0008-20 micrograms/ml for UV and fluorimetric detection, respectively. These methods were applied, without any interference from the excipients, for the determination of the drug in tablets and in drug dissolution studies. It is suggested that the proposed HPLC procedures could be used for routine quality control and dosage form assay of verapamil hydrochloride.

Study on electrooxidation of cefadroxil monohydrate and its determination by differential pulse voltammetry.

In this work electrooxidation of cefadroxil monohydrate was investigated using a glassy carbon electrode depending on pH and supporting electrolyte. It was shown that the direct determination of the substance from capsules and in oral suspension could be made by differential pulse voltammetry (DPV). UV and first derivative UV spectrophotometric methods are also proposed as comparative methods.

Anodic voltammetry of cefotaxime.

In this study electrooxidation of cefotaxime was investigated using specially activated glassy carbon (GC), platinum and carbon paste (CP) electrodes in different supporting electrolyte solutions and at different pHs. The data revealed that the shapes of the voltammograms and the numbers of the oxidation steps changed depending on the nature of the electrode. The nature of the supporting electrolyte was also important for the response of the electrode. From an analytical point of view, the activated GC electrode was the most favourable one. In 0.2 M H3PO4 with an activated GC electrode the calibration graph gave two lines with different slopes in the concentration ranges of 2 x 10(-5)-1 x 10(-4) and 2 x 10(-4)-6 x 10(-4). The results of the recovery test and statistical analysis showed that the voltammetric method could be used for the determination of cefotaxime.

Determination of terbutaline based on oxidation by voltammetry.

A voltammetric study of the oxidation of terbutaline has been carried out at an activated glassy carbon electrode. The compound was oxidized irreversibly at high positive potential. The response was evaluated with respect to pH, scan rate, nature of the buffer and other variables. The peak current, at about 0.8 V (versus a saturated calomel electrode), was proportional to the terbutaline concentration in the range of 8 x 10(-6)-8 x 10(-4) M in phosphate buffer pH 6.0. This method was applied, without any interferences from the excipients, to determine the drug in a tablet dosage form.

Voltammetric determination of droperidol and benperidol.

In this study two butyrophenones, droperidol and benperidol were voltammetrically investigated using platinum and specially activated glass carbon electrodes. The behaviours of the substance were investigated in various electrolyte solutions having different pH values and by different scan rates. As a result of the studies it was shown that the quantitative determinations of the substances from their pharmaceutical preparations could be made rapidly and simply without any separation from the excipients.

Determination of ornidazole in pharmaceutical dosage forms based on reduction at an activated glassy carbon electrode.

The electrochemical reduction of ornidazole was studied at a glassy carbon electrode activated by applying a new pretreatment. The dependence of intensities of currents and potentials on pH, concentration, scan rate, nature of the solvent (aqueous media, mixed aqueous-organic systems) and surfactant was investigated. Linear calibration plots were obtained over the concentration ranges 4x10(-6)-6x10(-4) and 6x10(-6)-6x10(-4) mol l(-1) in 0.2 M H(2)SO(4) and acetate buffer (pH 4.7), respectively. The method was applied to the determination of ornidazole in different drug formulations.

Anodic voltammetry of fluphenazine at different solid electrodes.

The electrochemical behaviour of fluphenazine based on its oxidation at platinum and glassy carbon electrodes was investigated by linear sweep and cyclic voltammetry. The influence of pH, concentration, nature of the buffer and scan rate was carefully examined. At both electrodes, three anodic steps (representing an irreversible oxidation) were obtained. The method was applied to the determination of fluphenazine in sugar-coated tablets.

Voltammetric determination of imipramine hydrochloride and amitriptyline hydrochloride using a polymer-modified carbon paste electrode.

In this paper the voltammetric behaviors of imipramine.HCl and amitriptyline. HCl, which are both tricyclic antidepressants, were investigated using a carbon paste electrode, modified by the addition of poly(N-vinylimidazole), in various solutions of different pHs. It was shown that the current density for imipramine increased with modification of the carbon paste electrode and amitriptyline, which was electroinactive with the normal carbon paste electrode, became electroactive on the modified electrode. The optimum conditions for the quantitive determination of imipramine.HCl and amitriptyline.HCl were determined and statistical analysis of the linear relationship between current and concentration is given. The method was applied for the determination of these substances in the pharmaceutical dosage forms.

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.

Investigation of the mechanism of the electrochemical oxidation of bamipine hydrochloride by voltammetry.

The electrochemical oxidation of bamipine hydrochloride in sulphuric acid and phosphate buffer solutions was examined using a platinum electrode. Two different reaction mechanisms for two different potential regions are proposed. It was shown that the determination of the drug by this method is feasible.

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.