Determination of 5-aminosalicylic acid in pharmaceutical formulations by square wave voltammetry at pencil graphite electrodes

An analytical method for the determination of the anti-inflammatory drug 5-aminosalicylic acid (5-ASA) in pharmaceutical formulations using square wave voltammetry at pencil graphite electrodes was developed. After the optimization of the experimental conditions, calibration curves were obtained in the linear concentration range from 9.78 × 10-7 to 7.25 × 10-5 mol L-1 resulting in a limit of detection of 2.12 ± 0.05 x 10-8 mol L-1. Statistical tests showed that the concentrations of 5-ASA in commercial tablets and enemas obtained with the proposed voltammetric method agreed with HPLC values at a 95% confidence level.

Análise voltamétrica da ciprofloxacina – aplicação a medicamentos e a remediação

O presente trabalho tem como objectivo o desenvolvimento de um método analítico, baseado na voltametria de onda quadrada (SWV), para a análise de ciprofloxacina (CIP) em produtos farmacêuticos e em processos de remediação. Para o desenvolvimento do método voltamétrico foram utilizadas duas células voltamétricas: a célula clássica (utilizando um eléctrodo de trabalho de carbono vítreo - GCE) e um eléctrodo de carbono impresso (SPCE). Após a optimização dos parâmetros da SWV, pH (3,04), frequência (400Hz), incremento de potencial (6 mV) e amplitude do impulso de potencial (40 mV), procedeu-se a validação dos métodos, obtendo-se zonas lineares entre a concentração de CIP e a intensidade de corrente de pico de 5,0×10-6 a 6,0×10-5 mol/L (GCE) e de 1,0×10-5 a 4,0×10-5 mol/L (SPCE) e limites de detecção de 9,48×10-6 mol/L (GCE) e 2,13×10-6 mol/L (SPCE). Verificou-se que a sensibilidade, a precisão e a selectividade são superiores para o SPCE, sendo por isso esta a célula mais adequada para proceder à análise da CIP em produtos farmacêuticos. O SPCE foi aplicado com sucesso à análise de CIP num produto farmacêutico. Para o tratamento de soluções aquosas contendo a CIP foram testados dois oxidantes: o permanganato de potássio e o peróxido de hidrogénio. Para o peróxido de hidrogénio os resultados obtidos foram inconclusivos. No caso do permanganato de potássio, os resultados mostram que a degradação da ciprofloxacina depende da concentração do oxidante. Para uma concentração de CIP de 3,00×10-4 mol/L uma degradação rápida foi obtida com o uso de 6,00×10-3 mol/L de permanganato de potássio. Na aplicação do permanganato na remediação de solos verificou-se que no caso de solos húmicos a ciprofloxacina é adsorvida pelo solo, não sendo possível confirmar a ocorrência da reacção de degradação. No caso de solos arenosos verificou-se que a ciprofloxacina foi rapidamente degradada pelo permanganato de potássio.

Electroanalytical study of the antidepressant sertraline

Aflowinjection squarewave cathodic stripping voltammetric method has been developed for the determination of sertraline in a pharmaceutical preparation. The method shows linearity between peak current intensity and sertraline concentration for the interval between 0.20×10−6 and 1.20×10−6 mol L−1. Limits of detection and quantification were found to be 1.5×10−7 and 5.0×10−7 mol L−1, respectively. Up to 70 samples per hour can be analysed with a good precision (R.S.D. = 2.5%). The proposed method was successfully applied to the determination of sertraline in a commercial product. In the voltammetric determination of sertraline in flow, a high sample rate is obtained at reduced costs, opening the possibility to compete with the chromatographic methods generally used for this analysis.

Electrochemical determination of the herbicide bentazone using a carbon nanotube b-Cyclodextrin modified electrode

An electrochemical sensor has been developed for the determination of the herbicide bentazone, based on a GC electrode modified by a combination of multiwalled carbon nanotubes (MWCNT) with b-cyclodextrin (b-CD) incorporated in a polyaniline film. The results indicate that the b-CD/MWCNT modified GC electrode exhibits efficient electrocatalytic oxidation of bentazone with high sensitivity and stability. A cyclic voltammetric method to determine bentazone in phosphate buffer solution at pH 6.0, was developed, without any previous extraction, clean-up, or derivatization steps, in the range of 10–80 mmolL 1, with a detection limit of 1.6 mmolL 1 in water. The results were compared with those obtained by an established HPLC technique. No statistically significant differences being found between both methods.

Eletroanálise de derivados acetaldeído com hidrazina e determinação em amostras de álcool combustível por voltametria de onda quadrada

A square wave voltammetric method is described for the determination of acetaldehyde using the derivatization reaction with hydrazine sulphate, based on the reduction of hydrazone generated as a product that exhibits a single well-defined peak at -1.19V in acetate buffer at pH 5. Calibration graphs were obtained from 1.0 x 10-6 mol L-1 to 10 x 10-6 mol L-1 of acetaldehyde, using a reaction time of 8 min and a hidrazine concentration of 0.02 mol L-1. The detection limit was 2.38 x 10-7 mol L-1. The method was applied satisfactorily to the determination of total aldehyde in fuel ethanol samples without any pre-treatment.

Determinação voltamétrica do herbicida glifosato em águas naturais utilizando eletrodo de cobre

The aim of this work was to investigate the copper electrode behavior in the voltammetric determination of glyphosate. The best conditions for this determination are phosphate buffer 0.05 mol L-1 and pH 7.3, and the peak potential is observed at 187 mV. LD and LQ values are 59 µg L-1 e 196 µg L-1, respectively. A water sample was analysed for glyphosate and identical results were obtained by using the analytical curve and the standard addition method. The comparison with a voltammetric method with Hg electrode, after a reaction with nitrite, showed quite concordant results for the analysis of the surface water sample. Therefore, the proposed method can be applied to direct determinations of the herbicide in waters, decreasing the time of analysis; besides, the method is in agreement with the "green chemistry" concept.

Determination of 5-aminosalicylic acid in pharmaceutical formulations by square wave voltammetry at pencil graphite electrodes

An analytical method for the determination of the anti-inflammatory drug 5-aminosalicylic acid (5-ASA) in pharmaceutical formulations using square wave voltammetry at pencil graphite electrodes was developed. After the optimization of the experimental conditions, calibration curves were obtained in the linear concentration range from 9.78 × 10-7 to 7.25 × 10-5 mol L-1 resulting in a limit of detection of 2.12 ± 0.05 x 10-8 mol L-1. Statistical tests showed that the concentrations of 5-ASA in commercial tablets and enemas obtained with the proposed voltammetric method agreed with HPLC values at a 95% confidence level.

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.

The use of a gold disc microelectrode for the determination of copper in human sweat

A novel approach of using a gold disc microelectrode to analyze sweat samples for copper ions by anodic square wave stripping voltammetry (SW stripping voltammetry) is described Sweat was collected from the lower back of four subjects after physical exercise and the sample volume required for the determinations was 100 mu L. Under the optimized conditions the calibration plot was linear over the range 1-100 mu mol L(-1) Cu(II) with a limit of detection of 0 25 mu mol L(-1) The precision was evaluated by carrying out five replicate measurements in a 1 mu mol L(-1) Cu(II) solution and the standard deviation was found to be 1 5% Measurements were performed by inserting the microelectrode into sweat drops and Cu(II) concentrations in the analyzed samples ranged from 09 to 28 mu mol L(-1) Values obtained by the proposed voltammetric method agreed well with those found using graphite furnace atomic absorption spectroscopy (GFAAS) (C) 2010 Elsevier B V All rights reserved

Activated Copper Cathodes as Sensors for Nitrite Analysis

The increased surface area of copper electrodes upon applying a suitable potential protocol was characterized by atomic force microscopy images. Scanning electrochemical microscopy was used to demonstrate the enhanced reactivity of the generated surface. The modified electrode showed excellent catalytic activity towards nitrite reduction in acidic medium (pH 2). This new platform was used in the development of a fast and simple voltammetric method for nitrite determination. Commercial and rainwater spiked samples were analyzed and the data showed an excellent agreement with those obtained with a reference spectrophotometric method (Griess reaction) at a confidence level of 95% (Student`s t-test).

Determination of 5-aminosalicylic acid in pharmaceutical formulations by square wave voltammetry at pencil graphite electrodes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Determination of isoniazid in human urine using screen-printed carbon electrode modified with poly-L-histidine

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Screen-Printed Carbon Electrode Modified with Poly-L-histidine Applied to Gold(III) Determination

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Copper determination in ethanol fuel samples by anodic stripping voltammetry at a gold microelectrode

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Eletroanálise de derivados acetaldeído com hidrazina e determinação em amostras de álcool combustível por voltametria de onda quadrada

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)