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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 reduction of luvastatin (FLV) at a hanging mercury-drop electrode (HMDE) was studied by square-wave adsorptive-stripping voltammetry (SWAdSV). FLV can be accumulated and reduced at the electrode, with a maximum peak current intensity at a potential of approximately -1.26 V vs. AgCl/Ag, in an aqueous electrolyte solution of pH 5.25. The method shows linearity between peak current intensity and FLV concentration between 1.0 × 10-8 and 2.7 × 10-6 mol L-1. Limits of detection (LOD) and quantification (LOQ) were found to be 9.9 × 10-9 mol L-1 and 3.3 × 10-8 mol L-1, respectively. Furthermore, FLV oxidation at a glassy carbon electrode surface was used for its hydrodynamic monitoring by amperometric detection in a flow-injection system. The amperometric signal was linear with FLV concentration over the range 1.0 × 10-6 to 1.0 × 10-5 mol L-1, with an LOD of 2.4 × 10-7 mol L-1 and an LOQ of 8.0 × 10-7 mol L-1. A sample rate of 50 injections per hour was achieved. Both methods were validated and showed to be precise and accurate, being satisfactorily applied to the determination of FLV in a commercial pharmaceutical. [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]

Electroanalytical methods based on square-wave adsorptive-stripping voltammetry (SWAdSV) and flow-injection analysis with square-wave adsorptive-stripping voltammetric detection (FIA-SWAdSV) were developed for the determination of fluoxetine (FXT). The methods were based on the reduction of FXT at a mercury drop electrode at -1.2 V versus Ag/AgCl, in a phosphate buffer of pH 12.0, and on the possibility of accumulating the compound at the electrode surface. The SWAdSV method was successfully applied in the quantification of FXT in pharmaceutical products, human serum samples, and in drug dissolution studies. Because the presence of dissolved oxygen did not interfere significantly with the analysis, it was possible to quantify FXT in several pharmaceutical products using FIA-SWAdSV. This method enables analysis of up to 120 samples per hour at reduced costs. [ABSTRACT FROM AUTHOR]

A methodology for the determination of the pesticide chlorfenvinphos by microwave-assisted solvent extraction and square-wave cathodic stripping voltammetry at a mercury film ultramicroelectrode in soil samples is proposed. Optimization of microwave solvent extraction performed with two soils, selected for having significantly different properties, indicated that the optimum solvent for extracting chlorfenvinphos is hexane-acetone (1:1, v/v). The voltammetric procedure is based on controlled adsorptive accumulation of the insecticide at the potential of-0.60 V (vs. Ag/AgCl) in the presence of Britton-Robinson buffer (pH 6.2). The detection limit obtained for a 10 s collection time was 3.0×10-8 mol l-1. The validity of the developed methodology was assessed by recovery experiments at the 0.100 µg g-1 level. The average recoveries and standard deviations for the global procedure reached by MASE-square-wave voltammetry were 90.2±2.8% and 92.1±3.4% for type I (soil rich in organic matter) and type II (sandy soil) samples, respectively. These results are in accordance to the expected values which show that the method has a good accuracy. [ABSTRACT FROM AUTHOR]

A detailed study of voltammetric behavior of ethiofencarb (ETF) is reported using glassy carbon electrode (GCE) and hanging mercury drop electrode (HMDE). With GCE, it is possible to verify that the oxidative mechanism is irreversible, independent of pH, and the maximum intensity current was observed at +1.20 V vs. AgCl/Ag at pH 1.9. A linear calibration line was obtained from 1.0×10 -4 to 8.0×10 -4 mol L -1 with SWV method. To complete the electrochemical knowledge of ETF pesticide, the reduction was also explored with HMDE. A well‐defined peak was observed at –1.00 V vs. AgCl/Ag in a large range of pH with higher signal at pH 7.0. Linearity was obtained in 4.2×10 -6 and 9.4×10 -6 mol L -1 ETF concentration range. An immediate alkaline hydrolysis of ETF was executed, producing a phenolic compound (2‐ethylthiomethylphenol) (EMP), and the electrochemical activity of the product was examined. It was deduced that it is oxidized on GCE at +0.75 V vs. AgCl/Ag with a maximum peak intensity current at pH 3.2, but the compound had no reduction activity on HMDE. Using the decrease of potential peak, a flow injection analysis (FIA) system was developed connected to an amperometric detector, enabling the determination of EMP over concentration range of 1.0×10 -7 and 1.0×10 -5 mol L -1 at a sampling rate of 60 h -1 . The results provided by FIA methodology were performed by comparison with results from high‐performance liquid chromatography (HPLC) technique and demonstrated good agreement with relative deviations lower than 4%. Recovery trials were performed and the obtained values were between 98 and 104%. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of citalopram was studied by square-wave and square-wave adsorptive-stripping voltammetry (SWAdSV). Citalopram can be reduced and accumulated at a mercury drop electrode, with a maximum peak current intensity being obtained at a potential of approximately - 1.25 V vs. AgCl/Ag, in an aqueous electrolyte solution of pH 12. A SWAdSV method has been developed for the determination of citalopram in pharmaceutical preparations. The method shows a linear range between 1.0 × 10-7 and 2.0 × 10-6 molL-1 with a limit of detection of 5 × 10-8molL-1 for an accumulation time of 30s. The precision of the method was evaluated by assessing the repeatability and intermediate precision, achieving good relative standard deviations in all cases (≤2.3%). The proposed method was applied to the determination of citalopram in five pharmaceutical products and the results obtained are in good agreement with the labeled values. [ABSTRACT FROM AUTHOR]

An extraction-adsorptive stripping voltammetric procedure for the determination of the pesticide dialifos in soil samples using microwave-assisted solvent extraction and a mercury film ultramicroelectrode was developed. The method is based on the use of hexane-acetone solvent (1:1, v/v) and on controlled adsorptive accumulation of the insecticide at the potential of -0.10V (versus Ag/AgCl) in the presence of Britton-Robinson buffer (pH 2.0). Soil sample extracts were analyzed directly after drying and redissolution with the supporting electrolyte, but without other pretreatment. The limit of detection obtained for a 10 sec collection time was 2.0 µ 10 -8 mol L-1. Recovery experiments for the global procedure, at the 0.100 µg g-1 level, gave satisfactory average and standard deviation results for the two different soils tested. [ABSTRACT FROM AUTHOR]

Microwave-assisted solvent extraction was combined with anodic adsorptive stripping voltammetry at a gold microelectrode to extract and quantify the herbicide atrazine in spiked soil samples. A systematic study of the experimental parameters affecting the stripping response was carried out by square-wave voltammetry. The voltammetric procedure is based on controlled adsorptive accumulation of atrazine at the potential of 0.35 V(versus Ag/AgCl) in the presence of Britton–Robinson buffer pH(2.0). The limit of detection obtained for a 30 sec collection time was 4.3 × 10−7 mol L−1. Recovery experiments, at the 1 µg g−1 level of spiking, gave good results for the global procedure, and the values found were comparable to those obtained by HPLC. [ABSTRACT FROM AUTHOR]

The analysis of opiates is of vital interest in drug abuse monitoring and research. This review presents a general overview of the electrochemical methods used for detection and quantification of opiates in a variety of matrices. Emphasis has been placed on the voltammetric methods used for study and determination of morphine, codeine, and heroin. Specific issues that need to be solved and better explained as well as future trends in the use of electrochemical methods in the examination of opiates are also discussed. [ABSTRACT FROM AUTHOR]

An adsorptive stripping voltammetric procedure for the determination of the antidepressant venlafaxine in urine using a mercury film microelectrode was developed. The method is based on controlled adsorptive accumulation of the drug at the potential of −1.00 V (vs. Ag/AgCl) in the presence of 1.25 × 10−2 mol L−1 borate buffer (pH 8.7). Urine samples were analyzed directly after performing a ten-fold dilution with the supporting electrolyte but without other pretreatment. The limit of detection obtained for a 30 s collection time was 0.693 × 10−6 mol L−1. Recovery experiments gave good results at the 10−6 mol L−1 level (bias less 5% were obtained). [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]