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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.

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 4×10−6–6×10−4 and 6×10−6–6×10−4 mol l−1 in 0.2 M H2SO4 and acetate buffer (pH 4.7), respectively. The method was applied to the determination of ornidazole in different drug formulations.

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.

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. (C) 1998 Elsevier Science B.V. All rights reserved.

In this study two butyrophenones, droperidol and benperidol were voltammetrically investigated using platinum and specially activated glassy carbon electrodes. The behaviours of the substances 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.

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.

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.