In this paper a novel supramolecular strategy to improve the efficiency of a voltammetric sensor to determine two biologically relevant molecules (epinephrine (EP) and uric acid (UA)) is presented. The strategy is based on the use of a glassy carbon electrode modified with a copper(II) complex ([Cu(H2dimpy)Cl]PF6) adsorbed on multi-walled carbon nanotubes (MWCNTs). The [Cu(H2dimpy)Cl]PF6/MWCNT composite-supported electrode was characterized by electrochemical impedance spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The electrocatalytic oxidation of EP and UA using the sensor was investigated by cyclic voltammetry and square wave voltammetry. Under optimized conditions, voltammetric peak currents showed a linear response for the EP and UA concentrations in the ranges 0.5-159.2 and 0.2-58.5 µmol L−1, whereas the limits of detection were 0.2 and 0.05 µmol L−1, respectively. The sensor was successfully applied in the selective and simultaneous determination of EP and UA in human urine samples. Thus, our results showed that the supramolecular strategy was successful to build an efficient sensor for simultaneous detection of these molecules in biological samples.

This work reports a simple and low cost voltammetric approach comprising a boron-doped diamond electrode (BDDE) to determine the antibiotic ethionamide (ETO). Cyclic voltammetry studies revealed that ETO exhibits an irreversible reduction peak at -0.95 V and an irreversible oxidation peak at +1.4 V onto BDDE (vs. saturated Ag/AgCl reference electrode) in Britton-Robinson buffer solution (pH 5.0, 0.1 mol L-1). Different voltammetric scan rates (from 10 to 150 mV s-1) suggested that the reduction of ETO on the BDDE surface is a diffusion-controlled process. Square wave voltammetry (SWV) optimized conditions showed a linear response to ETO from 1.00 to 80.0 µmol L-1 (R2 = 0.998) with a limit of detection of 0.294 µmol L-1 and limit of quantification of 0.980 µmol L-1. The developed square wave voltammetric method was successfully used in the determination of ETO in human urine and pharmaceutical formulation. The ETO quantification results in pharmaceutical tablets obtained by SWV-BDDE were comparable to those found by official analytical protocols.

<p>A simple and sensitive method using first-derivative ultraviolet spectrophotometry (DS-UV) was developed, validated, and compared to the high performance liquid chromatography (HPLC) method for quantification of paclitaxel (PTX) in a liposomal formulation. Different analytical performance parameters such as linearity, accuracy, precision, specificity, detection, and quantification limits were determined according to International Conference on Harmonization (ICH) guidelines. No interference from the lipid compounds was detected in the HPLC and the DS-UV methods at 246 nm. Linearity determined for paclitaxel concentrations ranging from 6.0 to 24.0 µg mL^-1 presented a correlation coefficient higher than 0.999 for both methods. Relative standard deviation (RSD) values lower than 2% for intra- and inter-day precision data could be obtained. Accuracy mean values ranged from 98.9 to 102.0%. Robustness data showed that the PTX content was unaffected by the alteration proposed. Both methods were adequate to quantify the drug in the liposomal formulation. DS-UV proved to be rapid, accurate, selective, sensitive, and, therefore, an attractive tool for routine determination of PTX.</p>

Advanced oxidative processes (AOPs) are based on chemical processes that can generate free radicals, such as hydroxyl radicals (.OH) which are strong, non-selective oxidant species that react with the vast majority of organic compounds. Nanostructured semiconductors, especially titanium dioxide (TiO2) in the anatase phase, are well-established photocatalysts for this process, which have proved to be useful in the degradation of dyes, pesticides and other contaminants. Research in different strategies for the synthesis of nanostructured semiconductors, with particular characteristic is currently a topic of interest in many studies. Thus, this paper presents a review about various synthesis strategies of nanostructured photocatalysts.

The aim of this work is to discuss some selected applications of square wave voltammetry published in the last five years. The applications focused here cover several electroanalytical fields such as: determination of pesticides; molecules with biological activity; metals and other environmental pollutants. Special attention is given to the work developed in the Grupo de Materiais Eletroquímicos e Métodos Eletroanalíticos - IQSC - USP concerning the utilization of square wave voltammetry, with different kinds of electrodes, for the determination of pesticides in natural waters and active principles in pharmaceutical formulations. The new methodology is simple, fast and sensitive when compared with the traditional ones such as chromatography and spectrophotometry. The satisfactory results obtained provide alternative procedures for the quality control of drugs and the monitoring of pesticides in natural environments.

O comportamento voltamétrico da ranitidina foi estudado em meio aquoso utilizando um ultramicroeletrodo de platina com eletro-depósito de mercúrio (Hg-UME) e o eletrodo de gota pendente de mercúrio, HMDE. A voltametria de varredura linear (LSV) mostrou que o composto apresenta duas ondas de redução em pH < 4,0 e somente uma em pH > 4,0, sendo as ondas observadas atribuídas à redução do grupo nitro para hidroxilamina. Foi observada uma relação linear entre a corrente de pico ou corrente limite e a concentração de ranitidina utilizando o HMDE ou o Hg-UME, demonstrando que a LSV com estes eletrodos pode ser utilizada na determinação analítica de ranitidina. Uma metodologia alternativa e mais sensível para determinação analítica de ranitidina utilizando a técnica SWV também foi desenvolvida, com um limite de detecção de 3,5 x 10-8 mol L-1 (ou 11 mg L-1). Os estudos de recuperação aparente (AR) mostraram a exatidão e precisão da metodologia desenvolvida. Os excipientes encontrados nos comprimidos de marca (Glaxo Wellcome) e genérico (EMSâ) não interferiram na determinação de ranitidina.

The voltammetric behavior of ranitidine has been studied in aqueous media with a mercury coated platinum ultramicroelectrode (Hg-UME) and by HMDE. The LSV curves for the electroreduction of ranitidine showed that the compound presents two reduction waves in pH < 4.0 and only one in pH > 4.0, the observed waves being attributed to the reduction of the nitro group to hydroxylamine. A linear relation between the current peak or limiting current and the ranitidine concentration using HMDE or Hg-UME was observed, demonstrating that these ultramicroelectrodes can be used in the analytical determination of ranitidine. An alternative and more sensitive methodology for the analytical determination of ranitidine by SWV was also developed, with a detection limit of 3.5 x 10-8 mol L-1 (or 11 mg L-1). The apparent recovery (AR) studies proved the accuracy and precision of the assay developed. The excipients found in comercial Antak tablets (Glaxo Wellcome) and the generic from EMSâ do not interfere in the determination.