Eduardo Henrique Duarte

A highly improved method for sensitive determination of amitriptyline in pharmaceutical formulations using an unmodified carbon nanotube electrode in the presence of sulfuric acid

The present paper describes a novel, simple and reliable differential pulse voltammetric method for determining amitriptyline (AMT) in pharmaceutical formulations. It has been described for many authors that this antidepressant is electrochemically inactive at carbon electrodes. However, the procedure proposed herein consisted in electrochemically oxidizing AMT at an unmodified carbon nanotube paste electrode in the presence of 0.1 mol L(-1) sulfuric acid used as electrolyte. At such concentration, the acid facilitated the AMT electroxidation through one-electron transfer at 1.33 V vs. Ag/AgCl, as observed by the augmentation of peak current. Concerning optimized conditions (modulation time 5 ms, scan rate 90 mV s(-1), and pulse amplitude 120 mV) a linear calibration curve was constructed in the range of 0.0-30.0 μmol L(-1), with a correlation coefficient of 0.9991 and a limit of detection of 1.61 μmol L(-1). The procedure was successfully validated for intra- and inter-day precision and accuracy. Moreover, its feasibility was assessed through analysis of commercial pharmaceutical formulations and it has been compared to the UV-vis spectrophotometric method used as standard analytical technique recommended by the Brazilian Pharmacopoeia.

Evaluation of a Multi-Walled Carbon Nanotube-Hemin Composite for the Voltammetric Determination of Hydrogen Peroxide in Dental Products

A simple, low cost sensor was developed for the voltammetric determination of hydrogen peroxide in mouthwash and dental whitening gel based on multi-walled carbon nanotubes incorporated with hemin. The sensor showed electrocatalytic activity toward the reduction of hydrogen peroxide in 0.05 mol L−1 Tris-HCl buffer solution (pH 7.0) using cyclic voltammetry. The optimum composition of paste was 20:10:70% (m/m/m) (multi-walled carbon nanotubes:hemin:mineral oil). A linear plot of the square root of scan rate vs. cathodic peak current showed that reduction of hydrogen peroxide is diffusion controlled. Using linear sweep voltammetry, the analytical curve ranged from 0.2 up to 1.4 mmol L−1 (r = 0.9996) with a sensitivity of 3.62 × 10−2 mA mol−1 L. The limits of detection and quantification were found to be 12.5 µmol L−1 and 41.7 µmol L−1, respectively. The developed method was applied for hydrogen peroxide determination in dental formulations. The results were compared with a volumetric method as a reference technique. No significant differences at the 95% level (paired student t test) were observed, thus demonstrating the accuracy of the sensor for the analysis of real samples.

Determinação voltamétrica de amitriptilina em formulações farmacêuticas com eletrodo de diamante dopado com boro explorando medidas em meio ácido

A simple and reliable voltammetric method is presented for the determination of amitriptyline using a boron-doped diamond electrode in 0.1 mol L-1 sulfuric acid solution as the support electrolyte. Under optimized differential pulse voltammetry conditions (modulation time 5 ms, scan rate 70 mV s-1, and pulse amplitude 120 mV), the electrode provides linear responses to amitriptyline in the concentration range 1.05 to 92.60 µmol L-1 and at a detection limit of 0.52 µmol L-1. The proposed method was successfully applied in pharmaceutical formulations, with results similar to those obtained using UV-vis spectrophotometric method as reference (at 95% confidence level), as recommended by the Brazilian Pharmacopoeia.Eduardo Henrique Duartea, Felipe Augusto Gorlaa, Elen Romão Sartoria e César Ricardo Teixeira Tarleya,b,* Departamento de Química, Centro de Ciências Exatas, Universidade Estadual de Londrina, Rodovia Celso Garcia Cid, PR 445 Km 380, 86050-482 Londrina – PR, Brasil Instituto Nacional de Ciência e Tecnologia de Bioanalítica, Departamento de Química Analítica, Instituto de Química, Universidade Estadual de Campinas, Cidade Universitária Zeferino Vaz s/n, 13083-970 Campinas – SP, Brasil

Voltammetric determination of amitriptyline in pharmaceutical formulation with boron-doped diamond electrode exploiting measures in acid medium

A simple and reliable voltammetric method is presented for the determination of amitriptyline using a boron-doped diamond electrode in 0.1 mol L-1 sulfuric acid solution as the support electrolyte. Under optimized differential pulse voltammetry conditions (modulation time 5 ms, scan rate 70 mV s-1, and pulse amplitude 120 mV), the electrode provides linear responses to amitriptyline in the concentration range 1.05 to 92.60 µmol L-1 and at a detection limit of 0.52 µmol L-1. The proposed method was successfully applied in pharmaceutical formulations, with results similar to those obtained using UV-vis spectrophotometric method as reference (at 95% confidence level), as recommended by the Brazilian Pharmacopoeia.Eduardo Henrique Duartea, Felipe Augusto Gorlaa, Elen Romão Sartoria e César Ricardo Teixeira Tarleya,b,* Departamento de Química, Centro de Ciências Exatas, Universidade Estadual de Londrina, Rodovia Celso Garcia Cid, PR 445 Km 380, 86050-482 Londrina – PR, Brasil Instituto Nacional de Ciência e Tecnologia de Bioanalítica, Departamento de Química Analítica, Instituto de Química, Universidade Estadual de Campinas, Cidade Universitária Zeferino Vaz s/n, 13083-970 Campinas – SP, Brasil