Showing papers on "Differential pulse voltammetry published in 1990"

Abrasive stripping voltammetric analysis of tin—bismuth

Abstract: The analysis of tin-bismuth alloys using a new stripping technique, abrasive stripping voltammetry, is described. Small amounts of the alloy are transferred by mechanical abrasion from the solid alloy onto the surface of a paraffin-impregnated graphite electrode. These traces are anodically stripped off with differential pulse voltammetry. The ratio of the tin and bismuth peak currents provide a measure of their relative content in the alloy. The determinations have standard deviations of about 5%. Peak potentials are reproducible within a 20-mV range.

Spectroelectrochemical characterization of nitridochromium(V) porphyrins and their reactivity with substituted acetic anhydrides

Abstract: The redox reactivity of a variety of nitridochromium(V) porphyrins was investigated by cyclic and differential pulse voltammetry as well as electronic and EPR spectroelectrochemical techniques. Each complex investigated underwent two single-electron reversible oxidation and two single-electron reversible reduction reactions at a Pt electrode in several nonaqueous solvents on the cyclic voltammetric time scale. The site of each electron-transfer reaction was centered on the porphyrin ring. This compares with the previously documented redox behavior of nitridomanganese(V) porphyrins but contrasts with the general redox behavior of chromium porphyrins

Differential Pulse Voltammetric Determination of Famotidine

Abstract: A differential pulse voltammetric method for the determination of famotidine in pharmaceutical preparations is described. The method is based on electrochemical oxidation of famotidine at a glassy carbon or platinum electrode. The proposed method shows good reproducibility, and sample preparation is simple.

Determination of Methimazole and Carbimazole Using Polarography and Voltammetry

Abstract: Anodic waves of methimazole (I) (1-methylimidazole-2-thiol) and carbimazole (II) (1-ethoxycarbonyl-3-methyl-2-thio-4-imidazoline) on mercury electrodes correspond to mercury salt formation. Both compounds form in the thiono form a soluble complex at pH < 6, compound (I) at higher pH-values a slightly soluble salt of the thiol form. Electrode processes involving the thiol form are complicated by adsorption. Oxidation at solid electrodes occurs only at potentials more than 0.5 V more positive. For compound (I) spectrophotometry indicated pKa=12.0 ± 0.2. By d.c. polarography in 0.1 M H2SO4 containing 10% ethanol the determination of both compounds is possible between 4 × 10− and 1 × 10−3 M, by differential pulse polarography between 1 × 10− and 1 × 10−4 M, by differential pulse voltammetry at HMDE between 5 × l0−7 and 6 × 10− M.

Determination of indole in shrimps by differential-pulse voltammetry in an emulsified medium

Abstract: A method has been developed to determine indole in shrimps by differential-pulse voltammetry at a Pt electrode in an emulsified medium, after extraction into hexane-ethyl acetate (49 + 1). The standard additions method was used in order to minimise the matrix effect. Recoveries at the concentration levels of 11.71 and 0.94 µg g–1 of shrimp were 82 and 75%, respectively. The relative standard deviations were 3.5 and 4.0%, respectively. The accuracy of the proposed method was verified by comparing the results obtained from the analysis of shrimp samples allowed to decompose at room temperature for 1, 3 and 4 d, with those obtained from a spectrophotometric method by applying Student's t-test.

Determination of Dopamine in Solution of Ascorbic Acid at Graphite-Reinforcement Carbon Electrodes by Differential Pulse Voltammetry

Abstract: Cyclic and differential pulse (DP) voltammograms of dopamine (DA) in Ringer's solution were measured at a graphite-reinforcement carbon (GRC) electrode. GRC is available as the lead of mechanical pencils. Cyclic voltammograms of DA exhibited two anodic peaks, at ca. -0.0 V and ca. 0.4 V vs. SCE, and a cathodic peak at 0.05 V vs. SCE in the solution of pH 6.8. Ascorbic acid (AA) presented an irreversible anodic wave at 0.2 V at pH 6.8. Voltammograms in the mixed solution of AA and DA were not a simple sum of each voltammogram, and hence were associated with chemical complications between AA and DA. DP voltammograms of the mixed solution had an anodic and a cathodic peak at ca. 0.05 V, which were stable during 4 days' soaking of the electrode in the solution. The anodic peak height was proportional to the concentration of DA in the range from 5.OX 10-6 to I .2X 10-4 mol dm-3. DA could be determined quantitatively from a calibration curve in the presence of AA from 5 to 20 times larger than DA concentrations.

Enhanced voltammetric waves of iron(III)—EDTA at a chitin‐containing carbon paste electrode and its analytical application

Abstract: A chitin-containing carbon paste electrode was found to give highly sensitive voltammetric waves for Fe(III)-EDTA chelate both in cyclic voltammetry (CV) and in differential pulse voltammetry (DPV). Various conditions for the determination of trace Fe(III) were studied. The optimum chitin content in the carbon paste (graphite powder: mineral oil = 2:1) was 6% (by weight). In a solution of 0.01 M KCl and 3 × 10−4 M EDTA (pH 3.0), the DPV peak potential for the reduction of Fe(III)-EDTA was −0.05 V vs. Ag/AgCl. The peak current was proportional to the Fe(III) concentration between 2 × 10−7 and 6.5 × 10−6 M; the relative standard deviation for 2 × 10−6 M Fe(III) was 2.6%. The method was fairly free from interference and could be applied to the determination of iron in both river and tap water.

The effect of the structure of the substituent in position ten on the voltammetric behaviour of phenothiazin derivatives

Abstract: The electrochemical oxidation of seven derivatives of phenothiazine substituted in position 10 on the phenothiazine skeleton has been studied in acetonitrile, using a platinum disc electrode. The electron donor properties of the derivatives that depend on the substituent structure and the presence of nucleophiles in acetonitrile were followed. The diffusion coefficients for the formation of the radical cations were from 10 −5 to 10 −6 cm 2 s −1 and depended on the concentration of the acid in acetonitrile medium. A determination of these substances has been proposed, using differential pulse voltammetry, with a detection limit of 1•10 −7 mol l −1

Analytical application of differential staircase voltammetry

Abstract: Differential staircase voltammetry is a technique which utilizes the measurements of the dc-component of differential pulse voltammetry. The analytical applicability of the method was estimated using some well-known electrochemical systems. It could be shown that the detection limits of differential staircase voltammetric determinations are almost equal those obtained with differential pulse voltammetry.

Electroanalytical study of pirimicarb by anodic voltammetry at a glassy carbon electrode in aqueous and acetonitrile media

Abstract: An electroanalytical study of the oxidation process of pirimicarb at a glassy carbon electrode using different voltammetric techniques was carried out. Two media were used: aqueous Britton-Robinson buffer and acetonitrile (0.1 mol L−1 Bu4NClO4). Studies using linear sweep voltammetry (LSV) at a rotating disk electrode show that the limiting current becomes nondiffusion controlled at concentrations higher than 6.0 × 10−5 mol L−1. Cyclic voltammetry showed an irreversible electrode process. The best detection and determination limits were obtained by differential pulse voltammetry at a stationary electrode in an acetonitrile medium. The differential pulse mode in an aqueous medium was used to determine pirimicab in soil samples.