Search

In this work electrooxidation of diethylstilbestrol (DES) was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) using a glassy carbon (GC) electrode. It was statistically shown that both methods could be used for the determination of DES in the concentration range of 2 x 10(-5)-6 x 10(-4) M by CV and 1 x 10(-5)-1 x 10(-3) M in methanol (MeOH) and 4 x 10(-5)-6 x 10(-4) M in acetonitrile (ACN) by DPV and both of the methods could be applied to human serum. A mechanism was proposed about the electrooxidation of this substance.

Electrooxidation of β-estradiol was investigated using a glassy carbon electrode (GCE) by cyclic voltammetry (CV), and differential pulse voltammetry (DPV). The statistical analysis of the linear relationships between concentration and peak current permits the quantitation of β-estradiol by both CV and DPV in the concentration range of 4×10 −5 –10 −3 M with enough precision and accuracy. A mechanism was proposed about the electrooxidation of this substance. The methods were applied to a tablet form and a transdermal therapeutic system (TTS) of this drug. The results were statistically compared with those of official high performance liquid chromatography (HPLC) method and the differences were found as insignificant.

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.

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 H 3 PO 4 with an activated GC electrode the calibration graph gave two lines with different slopes in the concentration ranges of 2×10 −5 –1×10 −4 and 2×10 −4 –6×10 −4 . The results of the recovery test and statistical analysis showed that the voltammetric method could be used for the determination of cefotaxime.

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 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 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.

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.