Novel electroanalysis of hydroxyurea at glassy carbon and gold electrode surfaces

A simple and a novel electroanalysis of hydroxyurea (HU) drug at glassy carbon and gold electrode was investigated for the first time using cyclic, linear sweep and differential pulse voltammetric techniques. The oxidation of HU was irreversible and exhibited a diffusion controlled process on both electrodes. The oxidation mechanism was proposed. The dependence of the current on pH, the concentration, nature of buffer, and scan rate was investigated to optimize the experimental conditions for the determination of HU. It was found that the optimum buffer pH was 7.0, a physiological pH. In the range of 0.01 to 1.0 mM, the current measured by differential pulse voltammetry showed a linear relationship with HU concentration with limit of detection of 0.46 µM for glassy carbon electrode and 0.92 µM for gold electrode. In addition, reproducibility, precision and accuracy of the method were checked as well. The developed method was successfully applied to HU determination in pharmaceutical formulation and human biological fluids. The method finds its applications in quality control laboratories and pharmacokinetics

Simultaneous electrochemical determination of acetaminophen and metoclopramide at electrochemically pre-treated disposable graphite pencil electrode

A sensitive and economic voltammetric method was developed for the simultaneous determination of acetaminophen (AMP) and metoclopramide (MCP) using pre-treated graphite pencil electrode (PTGPE). Compared to a graphite pencil electrode, the pre-treated electrode showed an apparent shift of the oxidation potentials in the positive direction and a notable enhancement in the current responses for both AMP and MCP. Cyclic voltammetry (CV) was used to study the voltammetric behavior of the drugs, while differential pulse voltammetry (DPV) was used to determine AMP and MCP simulta-neously. The dependence of the current on scan rate, pH and concentration was investi-gated to boost the experimental conditions for simultaneous determination. The calibra-tion curves were obtained over the range of 0.1×10-7 to 1.1×10-7 M, the concentration of each of both the drugs was varied by keeping the other constant, and achieved lower detection limit of 3.25 nM for AMP and 1.16 nM for MCP. The developed method was found to be selective, and rapid for the simultaneous determination of AMP and MCP. The proposed method was applied simultaneously in real samples and pharmaceutical samples, with satisfactory results

A kinetic and mechanistic study of oxidation of L-lysine by diperiodatonickelate(IV) in aqueous alkaline medium

1470-1475The kinetics of oxidation of L-lysine by diperiodatonickelate(IV) (DPN) in aqueous alkaline medium at a constant ionic strength of 0.60 mol dm-3 has been studied spectrophotometrically. The reaction shows first order in diperiodatonickelate(IV) and less than unit order dependence each in lysine and OH- ion concentrations. The addition of periodate retards the reaction, while the product nickel(II) do not show any significant effect on the reaction rate. An increase in ionic strength and decrease in dielectric constant of the medium decreases the rate. A mechanism based on experimental results is proposed. The constants involved in the mechanism are evaluated. The activation parameters with respect to slow step of the mechanism are computed and discussed

Electro-chemical oxidation and determination of granulocytosis risk inducing drug 4-aminoantipyrine at gold electrode

228-235A voltammetric technique for electrochemical sensing and quantification of granulocytosis risk inducing metabolite of aminopyrine, 4-Aminoantipyrine (4-AAP) at gold electrode has been developed. The gold electrode shows excellent selectivity and sensitivity towards the oxidation of 4-AAP in phosphate buffer solution (PBS) of pH=3.0. It is observed from the electrochemical studies of scan rate that overall electrode process is diffusion controlled and pH effect suggests involvement of protons in electrochemical oxidation of 4-AAP. A linear current response towards the electrochemical oxidation of 4-AAP in the concentration range of 1.0 × 10-6 – 2.5 × 10−5 M is observed with limit of detection of 3.8 × 10-8 M (S/N = 3). The interference studies have shown that the gold electrode exhibited excellent selectivity in presence of large excess of interferents. The method is employed to recovery study of 4-AAP in spiked urine and serum samples

Square wave and differential pulse voltammetric methods for the analysis of olivetol at gold electrode

Few electrochemical techniques have been employed for the determination of the powerful antitumor agent olivetol (OLV) in real samples at gold electrode. An intense and well pronounced oxidation peak was obtained at 1.04 V in the phosphate buffer pH 5.0 as the supporting electrolyte. The effects of pH and scan rate on the oxidation peak were studied. The electrochemical behavior of OLV was investigated using cyclic voltammetric (CV), square wave voltammetric (SWV) and differential pulse voltammetric (DPV) techniques. In DPV and SWV, the gold electrode showed a good sensitivity for OLV in a linear range of 0.1-1.5 μM and 0.1-1.3 μM and detection limits of 1.936×10-9 M and 4.754×10-9 M, respectively. A plausible mechanism involving an adsorption controlled oxidation reaction was deduced. The effect of various excipients was also studied and the method was successfully applied for the determination of OLV in human biological samples

Electro-chemical oxidation and determination of granulocytosis risk inducing drug 4-aminoantipyrine at gold electrode

A voltammetric technique for the electrochemical sensing and quantification of granulocytosis risk inducing metabolite of aminopyrine, 4-Aminoantipyrine (4-AAP) at a gold electrode (GE) was developed. The gold electrode showed excellent selectivity and sensitivity towards the oxidation of 4-AAP in phosphate buffer solution (PBS) of pH=3.0. It was observed from the electrochemical studies of scan rate that overall electrode process was diffusion controlled and pH effect suggested equal number of protons and electrons were involved in the electrochemical oxidation of 4-AAP. A linear current response towards the electrochemical oxidation of 4-AAP in the concentration range of 3.8 × 10-8 M and 1.61 × 10−7 M was observed with limit of detection of 3.8 × 10-8 M (S/N = 3). The interference studies showed that the gold electrode exhibited excellent selectivity in the presence of large excess of interferents. The method was employed to recovery study of 4-AAP in spiked urine and serum samples

Multi-spectroscopic characterization of bovine serum albumin upon interaction with atomoxetine

The quenching interaction of atomoxetine (ATX) with bovine serum albumin (BSA) was studied in vitro under optimal physiological condition (pH=7.4) by multi-spectroscopic techniques. The mechanism of ATX-BSA system was a dynamic quenching process and was confirmed by the fluorescence spectra and lifetime measurements. The number of binding sites, binding constants and other binding characteristics were computed. Thermodynamic parameters ∆H° and ∆S° indicated that intermolecular hydrophobic forces predominantly stabilized the drug-protein system. The average binding distance between BSA and ATX was studied by Försters theory. UV-absorption, Fourier transform infrared spectroscopy (FT-IR), circular dichroism (CD), synchronous spectra and three-dimensional (3D) fluorescence spectral results revealed the changes in micro-environment of secondary structure of protein upon the interaction with ATX. Displacement of site probes and the effects of some common metal ions on the binding of ATX with BSA interaction were also studied

ELECTRO-OXIDATION OF NIMESULIDE AT GOLD ELECTRODE AND ITS DETERMINATION IN PHARMACEUTICAL DOSAGE FORM AND HUMAN BIOLOGICAL FLUID

ABSTRACT The electro-oxidation of nimesulide has been investigated by cyclic and differential-pulse voltammetry at different pH at gold electrode. Cyclic voltammetric studies were performed in a wide range of sweep rates and various concentrations of nimesulide. The oxidation process was irreversible and exhibited a diffusion-controlled behavior. According to the linear relation between the peak current and the nimesulide concentration, differential-pulse voltammetric method for the quantitative determination in pharmaceuticals was developed. The recovery was determined to be 97.3 to 100.2 % by means of standard addition method. The linear response was obtained in the range of 2.0 x 10-7 to 1.2 x 10-6 M with a detection limit of 1.11 x 10-9 M with good selectivity and sensitivity. The electrochemical behaviors of nimesulide were studied and electron-transfer coefficient (α = 0.5), proton number (X = 1) and electron transfer number (n = 2) have been determined. The proposed method was also applied for the detection of nimesulide in urine as a real sample. Keywords: Nimesulide; Gold electrode; Electrochemical behavior; Drug analysi