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The electroactivity of butylate (BTL) is studied by cyclic voltammetry (CV) and square wave voltammetry (SWV) at a glassy carbon electrode (GCE) and a hanging mercury drop electrode (HMDE). Britton-Robinson buffer solutions of pH 1.9-11.5 are used as supporting electrolyte. CV voltammograms using GCE show a single anodic peak regarding the oxidation of BTL at +1.7 V versus AgCl/Ag, an irreversible process controlled by diffusion. Using a HMDE, a single cathodic peak is observed, at -1.0 V versus AgCl/Ag. The reduction of BTL is irreversible and controlled by adsorption. Mechanism proposals are presented for these redox transformations. Optimisation is carried out univaryingly. Linearity ranges were 0.10-0.50 mmol L-1 and 2.0-9.0 µmol L-1 for anodic and cathodic peaks, respectively. The proposed method is applied to the determination of BTL in waters. Analytical results compare well with those obtained by an HPLC method. [ABSTRACT FROM AUTHOR]

The electrooxidative behavior of citalopram (CTL) in aqueous media was studied by cyclic voltammetry (CV) and square-wave voltammetry (SWV) at a glassy-carbon electrode. The electrochemical behaviour of CTL involves two electrons and two protons in the irreversible and diffusion controlled oxidation of the tertiary amine group. The maximum analytical signal was obtained in a phosphate buffer (pH = 8.2). For analytical purposes, an SWV method and a flow-injection analysis (FIA) system with amperometric detection were developed. The optimised SWV method showed a linear range between 1.10 × 10-5-1.20 × 10-4 mol L-1, with a limit of detection (LOD) of 9.5 × 10-6 mol L-1. Using the FIA method, a linear range between 2.00 × 10-6-9.00 × 10-5 mol L-1 and an LOD of 1.9 × 10-6 mol L-1 were obtained. The validation of both methods revealed good performance characteristics confirming applicability for the quantification of CTL in several pharmaceutical products. [ABSTRACT FROM AUTHOR]

The electrochemical behaviour of the herbicide Asulam wets studied by cyclic and square wave voltammetry. Asulam may be irreversibly oxidised at a glassy carbon electrode. Maximum currents were obtained at pH = 1.9 in aqueous electrolyte solution. Based on the electrochemical behaviour of Asulam, two analytical methodologies were developed for its determination in water samples, using square wave voltammetry (SWV) and flow injection analysis (FIA) coupled with an amperometric detector. Limits of detection of 7.1 x 10[sup-6] molL[sup-1] and 1.2 x 10[sup-8] mol L[sup-1] for SWV and FIA respectively, were achieved. Repeatability was calculated by assessing the relative standard deviation (%) for 10 consecutive determinations of one sample. The found values were 2.1% for SWV and 5.0% for FIA. Validation of the results provided by SWV and FIA methodologies was performed by comparison with results from an HPLC-DAD technique. Good relative deviations were found (< 5%). Recovery trials were performed to assess the accuracy of the results and the obtained values were between 84% and 107% for both methods. [ABSTRACT FROM AUTHOR]

The electrooxidative behavior of pravastatin (PRV) in aqueous media was studied by square-wave voltammetry at a glassy-carbon electrode (GCE) and at a screen-printed carbon electrode (SPCE). Maximum peak current intensities in a pH 5.0 buffer were obtained at +1.3 V vs. AgCl/Ag and +1.0 V vs. Ag for the GCE and SPCE surface respectively. Validation of the developed methodologies revealed good performance characteristics and confirmed their applicability to the quantification of PRV in pharmaceutical products, without significant sample pretreatment. A comparative analysis between the two electrode types showed that SPCEs are preferred as an electrode surface because of their higher sensitivity and the elimination of the need to clean the electrode's surface for its renewal, which frequently is, if not always, the rate-limiting step in voltammetric analysis. [ABSTRACT FROM AUTHOR]

• First time a selective MIP electrochemical sensor was developed for Furazolidone (FZD). • QM calculations and MD simulations were used to select the best functional monomer and the optimum polymerisation conditions. • The sensor constructed based on MIP-CPE-MWCNTs showed high selectivity and sensitivity. • The proposed sensor was successfully applied for FZD detection in water samples without any pre-treatment step. Determination of antibiotics in environmental waters is an important global issue. Although furazolidone (FZD) was banned from use in food-producing animals, owing to its mutagenic and carcinogenic effects, this antibiotic has been illegally used across the world and its presence in environment have being noted. In this work, the first selective molecularly imprinted polymer (MIP) was developed for electrochemical detection of FZD. It was constructed based on the modification of the traditional carbon paste electrode (CPE) with MIP microparticles, followed by introduction of multi-walled carbon nanotubes (MWCNTs). Quantum mechanical (QM) calculations and molecular dynamics (MD) simulations were performed to allow rational selection of an appropriate functional monomer and to simulate the best pre-polymerisation conditions, respectively. The MIP were synthetized by polymerization using 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) as monomer and FZD as template molecule. The MIP microparticles were then incorporated on CPE-MWCNTs and the electrochemical analysis of FZD were evaluated by differential pulse voltammetry (DPV). After optimisation of experimental conditions, the MIP-CPE-MWCNTs sensor exhibited a good linear response over the concentration range of 0.01 μM to 1 μM with a correlation coefficient of 0.9995. The limit of detection (LOD) was found to be 0.03 μM (S/N = 3). Due to high imprinting efficiency the sensor displayed selectivity to recognise FZD molecules and it was successfully applied in water samples where excellent recovery values (over 90 %) were obtained. The proposed sensor provides an efficient and promising sustainable strategy for monitorisation of FZD in environmental waters. [ABSTRACT FROM AUTHOR]