Study of the electrochemical reduction of amoebicide Teclozan and its amperometric determination in pharmaceutical formulations

Neste trabalho, a redução eletroquímica do amebicida Teclozan (TEC) foi estudada sobre um eletrodo de carbono vítreo em meio de acetonitrila. Eletrólises com potencial controlado foram realizadas visando, tanto a determinação do número de elétrons envolvidos na redução do fármaco, quanto a identificação dos produtos eletrogerados, os quais foram isolados por extração líquido-líquido e caracterizados por 1H RMN. Foi verificado que o TEC apresenta dois picos voltamétricos, cada um associado à quebra redutiva de duas ligações C-Cl. Em presença de um doador de prótons, foi observado que o primeiro pico voltamétrico em −1,8 V corresponde principalmente à redução dos grupamentos -CHCl2 a -CH2Cl; enquanto o segundo pico em −2,2 V é responsável pela redução dos grupos -CH2Cl a CH3, fornecendo como único produto o derivado totalmente desalogenado do TEC, com rendimentos entre 82 e 97%. Este trabalho descreve também o desenvolvimento de um método eletroanalítico baseado na detecção amperométrica do TEC em condições hidrodinâmicas, o qual forneceu um limite de detecção de 8,9 × 10-6 mol L-1.The electrochemical reduction of amoebicide Teclozan (TEC) was studied on a glassy carbon electrode in acetonitrile. Controlled-potential electrolyses were performed for coulometric and preparative purposes. The electrogenerated products were isolated by liquid-liquid extraction and characterized by 1H NMR. It was observed that TEC presents two voltammetric peaks, each one associated with the cleavage of two C-Cl bonds. In presence of a proton donor it was observed that the first peak at −1.8 V promotes mainly the reduction of the groups CHCl2 to CH2Cl and the second one at −2.2 V promotes the reduction of the groups CH2Cl to CH3 giving as the sole product the completely dechlorinated TEC derivative with yields between 82 and 97%. In addition, a comparative study between the analytical performance of voltammetric techniques and amperometric detection of TEC in hydrodynamic conditions was performed. The amperometric detection was more sensitive than all evaluated voltammetric techniques, providing a detection limit of 8.9 × 10-6 mol L-1.FAPESP; CAPES; FC

Electrooxidation and determination of dopamine using a Nafion®-cobalt hexacyanoferrate film modified electrode

The electrocatalysis of dopamine has been studied using a cobalt hexacyanoferrate film (CoHCFe)-modified glassy carbon electrode. Using a rotating disk CoHCFe-modified electrode, the reaction rate constant for dopamine was found to be 3.5 × 105 cm3 mol-1 s-1 at a concentration of 5.0 × 10-5 mol L-1. When a Nafion® film is applied to the CoHCFe-modified electrode surface a high selectivity for the determination of dopamine over ascorbic acid was obtained. The analytical curve for dopamine presented linear dependence over the concentration range from 1.2 × 10-5 to 5.0 × 10-4 mol L-1 with a slope of 23.5 mA mol-1 L and a linear correlation coefficient of 0.999. The detection limit of this method was 8.9 × 10-6 mol L-1 and the relative standard deviation for five measurements of 2.5 × 10-4 mol L-1 dopamine was 0.58%

Electrochemical and theoretical evaluation of the interaction between dna and amodiaquine: evidence of the guanine adduct formation

The electrochemical behavior of the interaction of amodiaquine with DNA on a carbon paste electrode was studied using voltametric techniques. In an acid medium, an electroactive adduct is formed when amodiaquine interacts with DNA. The anodic peak is dependent on pH, scan rate and the concentration of the pharmaceutical. Adduct formation is irreversible in nature, and preferentially occurs by interaction of the amodiaquine with the guanine group. Theoretical calculations for optimization of geometry, and DFT analyses and on the electrostatic potential map (EPM), were used in the investigation of adduct formation between amodiaquine and DNA

Detection of Several Carbohydrates Using Boron-doped Diamond Electrodes Modified with Nickel Hydroxide Nanoparticles

In this work the electrooxidations of glucose, galactose, mannose, rhamnose, xylose and arabinose are studied at a nickel hydroxide nanoparticle modified boron-doped diamond electrode and compared to an unmodified electrode. These carbohydrates are very important in the second-generation ethanol production process. Nickel hydroxide modified boron-doped diamond was characterized by scanning electron microscopy and energy dispersive X-ray. Electrochemical impedance spectroscopy was employed to study the interface properties of surface-modified electrodes in the absence and presence of the carbohydrates. Limits of detection were 5.3 × 10(-5), 6.8 × 10(-5), 2.7 × 10(-4), 6.9 × 10(-5), 8.8 × 10(-5) and 2.6 × 10(-5) mol L(-1) for glucose, galactose, mannose, rhamnose, arabinose, xylose, respectively.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científco e Tecnológico (CNPq

Electrochemical reduction and voltammetric determination of diloxanide furoate in non-aqueous medium

The electrochemical reduction of diloxanide furoate (DF) in acetonitrile on glassy carbon electrode was studied in this work. It was observed that DF is reduced after a reversible one-electron transfer followed by an irreversible chemical reaction, diagnosed as C-Cl bond cleavage. Its reduction was followed by linear (LSV), differential pulse (DPV) and square wave voltammetry (SWV). Analytical curves were obtained for DF determination using all the investigated voltammetric techniques. For LSV was obtained a linear range (LR) from 5.0 x 10-4 to 1.0 x 10-2 mol L-1, with detection limit (DL) of 1.5 x 10-4 mol L-1 and sensitivity (S) of 2.1 x 10(4) µA mol-1 L. The analytical parameters obtained by DPV were: LR = 5.0 x 10-4 to 2.2 x 10-3 mol L-1, DL = 7.8 x 10-5 mol L-1, S = 3.7 x 10(4) µA mol-1 L. For SWV were obtained a LR = 7.5 x 10-6 to 1.2 x 10-3 mol L-1, DL = 5.5 x 10-6 mol L-1 and S = 2.8 x 10(5) µA mol-1 L. Thus, the SWV was the most sensible technique, which can be used for DF determination at low concentration levels. Statistics methods were used to evaluate the analytical procedure, where recovery around to 100% was obtained for all voltammetric techniques. Relative standard deviations were lower than 5.0% (N=5). The obtained t values evaluating all the three voltammetric methods were less than the tabulated ones, indicating that there are no evidences of systematic error