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Phenol is a toxic compound present in a wide variety of foundry resins. Its quantification is important for the characterization of the resins as well as for the evaluation of free contaminants present in foundry wastes. Two chromatographic methods, liquid chromatography with ultraviolet detection (LC-UV) and gas chromatography with flame ionization detection (GC-FID), for the analysis of free phenol in several foundry resins, after a simple extraction procedure (30 min), were developed. Both chromatographic methods were suitable for the determination of phenol in the studied furanic and phenolic resins, showing good selectivity, accuracy (recovery 99-100%; relative deviations <5%), and precision (coefficients of variation <6%). The used ASTM reference method was only found to be useful in the analysis of phenolic resins, while the LC and GC methods were applicable for all the studied resins. The developed methods reduce the time of analysis from 3.5 hours to about 30 min and can readily be used in routine quality control laboratories. [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]

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]

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]

Few analytical methods are currently available for determination of apomorphine, the active substance of a new oral formulation used in the treatment of erectile dysfunction. In this way a flow injection electrochemical method (FIA-EC) was developed for its quantification and applied to pharmaceutical dosage forms. Based in previous findings regarding the stability of apomorphine in borate buIer and after optimization of several analytical parameters a single channel flow injection manifold was set up that enables the determination of this drug over the concentration range of 3 to 16 μmol L[SUP-1] with a detection limit of 0.5 μmol L[SUP-1] at a sampling rate of 90 h[SUP-1]. The simplicity and rapidity of the FIA-EC method used, its reproducibility and sensitivity make it suitable for quality control of pharmaceutical preparations of apomorphine intended for clinical use and research. [ABSTRACT FROM AUTHOR]

A square wave voltammetric (SWV) method and a flow injection analysis system with electrochemical detection (FIA-EC) using a glassy carbon electrode were evaluated for the determination of codeine in pharmaceutical preparations. The interference of several compounds, such as acetaminophen, guaiacol, parabens, ephedrine, acetylsalicylic acid and caffeine, that usually appear associated with codeine pharmaceutical preparations was studied. It was verified that these electroanalytical methods could not be used with acetaminophen present in the formulations and that with guaiacol, parabens or ephedrine present the use of the FIA-EC system was impracticable. A detection limit of 5 µmol L-1 and a linear calibration range from 40 to 140 µmol L-1 was obtained with the SWV method. For the flow injection analysis procedure a linear calibration range was obtained from 7 to 50 µmol L-1 with a detection limit of 3 µmol L-1 and the FIA-EC system allowed a sampling rate of 115 samples per hour. The results obtained by the two methods, SWV and FIA-EC, were compared with those obtained using reference methods and demonstrated good agreement, with relative deviations lower than 4%. [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]

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]

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]

A SPME-GC-MS/MS method for the determination of eight organophosphorus pesticides (azinphos-methyl, chlorpyriphos, chlorpyriphos-methyl, diazinon, fenitrothion, fenthion, malathion, and methidathion) in still and fortified wine was developed. The extraction procedure is simple, solvent free, and without any sample pretreatment. Limits of detection (LOD) and quantitation (LOQ) values in the range 0.1-14.3 µg/L and 0.2-43.3 µg/L, respectively, were obtained. The LOQ values are below the maximum residue levels (MRLs) established by European Regulation for grapes, with the exception of methidathion. Coefficients of correlation (R2) higher than 0.99 were obtained for the majority of the pesticides, in all different wines analyzed. [ABSTRACT FROM AUTHOR]

Seven pyrethroids (bifenthrin, fenpropathrin, λ-cyhalothrin, permethrin, α-cypermethrin, fenvalerate, and deltamethrin) were extracted from water using C18 solid-phase extraction disks, followed by gas chromatography with an electron capture detector (GC-ECD) analysis. The limits of detection in water samples ranged from 0.5 ng L-1 (fenpropathrin) to 110 ng L-1 (permethrin), applying the calibration graph. The effects of different numbers of (re)utilizations of the same disks (up to four times with several concentrations) on the recoveries of the pyrethroids were considered. The recoveries were all between 70 and 120% after four utilizations of the same disk. There was no difference between these recoveries at a confidence level of 95%. [ABSTRACT FROM AUTHOR]

An analytical method, based on microwave-assisted extraction and liquid chromatography with diode array detection, for the determination of six carbamate and three urea pesticides in fresh and processed tomato samples is described. Significant parameters affecting extraction efficiency were optimized. Under optimum microwave-assisted extraction conditions (20 mL acetonitrile, for 10 minutes, at 60°C), pesticides were extracted with recoveries ranging from 57.6 to 102% (RSDs < 7%). Quantification limits between 6.5 and 39.6 µg/kg were obtained. A total number of 28 different fresh tomato samples and 6 processed tomato products were analysed. Confirmation of suspicious samples was performed by LC-MS. [ABSTRACT FROM AUTHOR]

A multiresidue approach using microwave-assisted extraction and liquid chromatography with photodiode array detection was investigated for the determination of butylate, carbaryl, carbofuran, chlorpropham, ethiofencarb, linuron, metobromuron, and monolinuron in soils. The critical parameters of the developed methodology were studied. Method validation was performed by analyzing freshly and aged spiked soil samples. The recoveries and relative standard deviations reached using the optimized conditions were between 77.0±0.46% and 120±2.9% except for ethiofencarb (46.4±4.4% to 105±1.6%) and butylate (22.1±7.6% to 49.2±11%). Soil samples from five locations of Portugal were analysed. [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]

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]