The aim of this manuscript is to develop a combined method for the detection and elimination of oxalic acid (OA) in aqueous environment. For that, the surface of glassy carbon (GC) electrode has been modified by oxidation of L‐cysteine using cyclic voltammetric (CV) technique. After modification, the formation of a compact and uniform cysteic acid layer film was achieved and it was confirmed by surface analysis (scanning electron microscopy (SEM) and atomic force microscopy (AFM)). Estimation of the linear range, calibration function and limit of detection for OA were performed by differential pulse voltammetry using Cysteine‐modified electrode (Cysteine‐MGC). Due to its stability and sensitive response to OA, it was used for monitoring OA during its electrochemical oxidation at Ti/Pt anode. DPV analyses have been compared with classic titration method and HPLC achieving a good fit, confidence intervals and limits. The results are described and discussed in the light of the existing literature.

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A simple differential pulse voltammetric method based on a graphite paste electrode (GPE) was developed for the quantitative determination of folic acid (FA) in tablets. The electrode exhibits a clear improvement of the current response. A linear response in the electroanalytical approach exists from 4.97×10−6 to 2.94×10−5 mol L−1 with a limit of detection of about 2.67×10−6 mol L−1 in KCl solutions. The developed procedure was tested by recovery studies and compared with spectrophotometric and chromatographic methods. The results are described and discussed in the light of existing literature.

In the present paper, differential pulse voltammetry (DPV) techniques has been studied for monitoring of the concentration of oxalic acid (OA) during its electrochemical oxidation (EO) in acidic media at BDD anode applying a current of 60 mA cm 2 . Glassy carbon has been used for DPV measurements using two analytical procedures: calibration curves (DPVCC) and standard addition method (DPVSAM). DPV analyses have compared with classic titration method and HPLC achieving a good fit, confidence intervals and limits

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The present study utilized thermogravimetry (TG) and optical emission spectroscopy with inductively coupled plasma (ICP/OES) to determine the amount of calcium in calcium citrate tablets, which are used for the treatment of osteoporosis. The samples were characterized using Fourier transform infrared spectroscopy (FTIR), termogravimetry/derivative thermogravimetry (TG/DTG), differential thermal analysis (DTA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). In the DTA and DSC curves obtained, both endo-and exothermic events were observed, which are indicative of dehydration and decomposition, respectively. The X-ray diffractograms showed that the samples present crystallinity. Additionally, peaks observed in the X-ray diffractograms indicate the presence of a calcium hydroxide residue due to the reaction between calcium oxide with moisture in the air. The calcium content obtained by TG from the tablet sample (17.77%) was similar to that obtained using ICP-OES (16.84%).

Resumo O presente estudo utilizou as técnicas termoanalíticas (TG e DSC) para avaliar o comportamento térmico de medicamentos a base de ácido acetilsalicílico comercializados como referência, genérico e similar. As amostras foram também caracterizadas por IV e DRX. As curvas TG/DTG mostraram comportamentos semelhantes, sendo verificadas, algumas variações, devido a presença dos excipientes nas formulações farmacêuticas. As curvas DSC apresentaram um pico endotérmico característico da fusão do ácido acetilsalicílico em todas as amostras. Os difratogramas de raios X mostraram similaridades, caracterizando as amostras como cristalinas.

Abstract:Chlorination is the most used method in the world for drinking water disinfection. However, the identification of by-products potentially toxics generated by this method has encouraged the development of new alternative disinfection technologies. Among them, heterogeneous photocatalysis, TiO 2 photocatalysis and electrochemical disinfection are considered as suitable alternatives to replace the chlorination method. This review article gives a general overview about these treatment systems that can contribute to drinking water disinfection and it shows the efficiency of recently developed free-chlorine systems.Keywords: Disinfection water; electrochemistry; photochemistry; chlorination; microorganisms. ResumoA cloração é o método mais usado no mundo para a desinfecção de água potável. No entanto, a identificação de subprodutos potencialmente tóxicos gerados por este método tem estimulado o desenvolvimento de novas tecnologias alternativas de desinfecção. Entre elas, fotocatálise heterogênea, fotocatálise de TiO 2 e desinfecção eletroquímica são consideradas alternativas adequadas para substituir o método de cloração. Este artigo de revisão dá uma visão geral sobre estes sistemas de tratamento eletroquímico que podem contribuir para a desinfecção de água potável o que mostra eficiência dos sistemas livres de cloro recentemente desenvolvidos.