Abstract:The present work presents a simple and didactic approach regarding some concepts involved in voltammetric techniques, starting from some basic principles of electrochemistry and advancing to the field of electroanalysis, passing through a discussion of mass transport phenomena, and culminating in a breakdown between different types of voltammetric techniques.Keywords: Voltammetry; electrochemical; mass transport. ResumoO presente trabalho apresenta uma abordagem simples e didática sobre conceitos envolvidos nas técnicas voltamétricas, partindo de alguns princípios básicos de eletroquímica e avançando para o campo da eletroanálise, passando por uma discussão sobre os fenômenos de transporte de massa e culminando numa classificação entre os diferentes tipos de técnicas voltamétricas.Palavras-chave: Voltametria; eletroquímica; transporte de massa.

A graphite-polyurethane composite electrode has been used for the determination of furosemide, a antihypertensive drug, in pharmaceutical samples by anodic oxidation. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the electrooxidation process at þ 1.0 V vs. SCE over a wide pH range, with the result that no adsorption of analyte or products occurs, unlike at other carbon-based electrode materials. Quantification was carried out using cyclic voltammetry, differential pulse voltammetry, and square-wave voltammetry. Linear ranges were determined (up to 21 mmol L À1 with cyclic voltammetry) as well as limits of detection (0.15 mmol L À1 by differential pulse voltammetry). Four different types of commercial samples were successfully analyzed. Recovery tests were performed which agreed with those obtained by spectrophotometric evaluation. The advantages of this electrode material for repetitive analyzes, due to the fact that no electrode surface renewal is needed owing to the lack of adsorption, are highlighted.

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Antifungal and trypanocidal aryl-1,4-naphthoquinones were prepared through an aqueous Suzuki protocol with reflux or microwave irradiation.

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A graphite-paraffin composite electrode has been used for the determination of ethambutol, an antituberculosis drug, in pharmaceutical samples by anodic oxidation. Voltammetric studies were used to characterise the electrochemical behaviour of the ethambutol in different pH solutions (3.0, 8.0 and 12.0). Quantification was carried out using amperometric detection. The detector was assembled in a flow injection apparatus and operated at + 1.1 V (vs. Ag/AgCl (NaCl,sat) ). The conditions for the best electrodes response were determined by studying the influence of sample volume and flow rate. The linear response for the method was extended up to a 1.5 mmol L À1 ethambutol solution with a detection limit of 0.1 mmol L À1. The repeatability for successive injections of 1.0 mmol L À1 ethambutol solution was 0.9 % (n = 26), demonstrating a good performance of the developed amperometric sensor. The analytical frequency was calculated as approximately 47 determinations h À1. Two different commercial samples were successfully analysed and the results were in good agreement with those obtained by using spectrophotometry. The advantages of the proposed amperometric method over the reference method include simplicity, low consumption of reagents and increased analytical frequency.

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