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URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11800
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Item DLLME-GC/ECD Method for the Residual Analysis of Parathion-Methyl and its Application in the Study of the UV-Photodegradation Process(Journal of the Brazilian Chemical Society, 2017-11) Pimenta, Gustavo G.; Queiroz, Maria E. L. R. de; Victor, Raquel P. D.; Noronha, Luiz M.; Neves, Antônio A.; Oliveira, André F. de; Heleno, Fernanda F.A new method has been developed to determine trace levels of organophosphorus pesticide parathion-methyl in water samples by using dispersive liquid-liquid microextraction (DLLME), followed by gas chromatograph coupled with electron capture detector (GC/ECD) analysis. The optimized and validated method showed high extraction recovery (101.1%), high enrichment factor (57.3), low limits of detection and quantification, 0.083 and 0.250 µg L-1, respectively. The established DLLME-GC/ECD method has been successfully applied for the evaluation of the photodegradation of the parathion-methyl by UV254nm radiation in different conditions of pH and temperature. The parathion-methyl photodegradation at pH 3 and 35 °C achieved > 99.5% after 120 min of exposition. For this condition, it was observed the kinetic rate of 0.0515 min-1, the quantum yield of 1.22 × 10-5 mol Einstein-1 and a half-life time of 13.46 min. All experimental conditions tested proved to be strongly influenced by pH and temperature. The application of the optimized process in distilled and drinking water spiked with parathion-methyl provided residues of this pesticide at levels below the maximum permitted by Brazilian legislation, which is 9.0 µg L-1.Item Determination of pesticides in lettuce using solid–liquid extraction with low temperature partitioning(Food Chemistry, 2015-02-20) Costa, Anna I.G.; Queiroz, Maria E.L.R.; Neves, Antônio A.; Sousa, Flaviane A. de; Zambolim, LaércioThis work describes the optimization and validation of a method employing solid–liquid extraction with low temperature partitioning (SLE/LTP) together with analysis by gas chromatography with electron capture detection (GC/ECD) for the determination of nine pesticides (chlorothalonil, methyl parathion, procymidone, endosulfan, iprodione, λ-cyhalothrin, permethrin, cypermethrin, and deltamethrin) in lettuce. The method was found to be selective, accurate, and precise, with means recovery values in the range of 72.3–103.2%, coefficients of variation ⩽12%, and detection limits in the range 0.4–37 μg kg−1. The matrix components significantly influence the chromatographic response of the analytes (above 10%). The optimized and validated method was applied to determine the residual concentrations of the fungicides iprodione and procymidone that had been applied to field crops of lettuce. The maximum residual concentrations of the pesticides in the lettuce samples were 13.6 ± 0.4 mg kg−1 (iprodione) and 1.00 ± 0.01 mg kg−1 (procymidone), on the day after application of the products.Item An optimized and validated 1H NMR method for the quantification of α-pinene in essentials oils(Talanta, 2015-10-31) Cerceau, Cristiane I.; Barbosa, Luiz C.A.; Filomeno, Claudinei A.; Alvarenga, Elson S.; Demuner, Antônio J.; Fidencio, Paulo H.The authenticity and composition of commercial essential oils requires strict quality control. Due to the importance of α-pinene containing essential oils, a rapid and efficient method for quantification of this terpene in oils of eucalyptus, pink pepper and turpentine using 1H NMR was developed and validated. All evaluated parameters (selectivity, linearity, accuracy/precision, repeatability, robustness, stability of analyte and internal standard in solutions) showed satisfactory results. The limit of detection (LOD) and limit of quantification (LOQ) were 0.1 and 2.5 mg respectively. These values indicated that α-pinene was detected in 35 mg samples containing at least 0.3% of this compound. In addition, a minimum of 8% of α-pinene in the sample was required for quantification. Furthermore, the standard deviations found in the 1H NMR methodology were less than 1% and were lower than those obtained by gas chromatographic analysis. Statistical tests have shown that the results obtained by 1H NMR methodology are similar to those obtained by GC-FID technique using external and internal standardization and normalization within 95% confidence. R&R values lower than 10% have shown that all the methods are appropriate and the 1H NMR method is suitable for quantification of α-pinene in samples of essential oils since this method possessed the smallest R&R (1.81) value.Item A validated 1 H NMR method for quantitative analysis of α -bisabolol in essential oils of Eremanthus erythropappus(Talanta, 2016-08-10) Cerceau, Cristiane I.; Barbosa, Luiz C.A.; Alvarenga, Elson S.; Ferreira, Antonio G.; Thomasi, Sérgio S.α-Bisabolol is a natural terpene produced by Eremanthus erythropappus and is widely used in cosmetics and pharmaceuticals due to its anti-inflammatory, antibacterial and antimycotic properties. Due to these applications, a control of composition and authenticity of commercial oils rich in this terpene is required, resulting in a demand for new methodologies for quality control. In this work a rapid and efficient method for quantification of α-bisabolol in the essential oil of E. erythropappus (candeia) using 1H NMR was developed, validated and compared to gas chromatography (GC) method. The quantification of α-bisabolol by 1H NMR was successfully achieved for most of the essential oil samples of E. erythropappus evaluated, except for those with a more complex composition. To circumvent this limitation a 2D NMR COSY contour map was used. This method proved to be a fast and efficient alternative, providing results with standard deviations SD<0.3%. All evaluated parameters (selectivity, linearity, accuracy/precision, repeatability, robustness and stability of analyte and internal standard in solution) gave satisfactory results. Using the 1H NMR signals at 5.36 and 5.13 ppm, the limit of detection (LOD) and limit of quantification (LOQ) were 0.26 and 2.59 mg, respectively. The results obtained by the 1H NMR method presented SD=0.59%, smaller than the value found for GC (SD=1.18%). Tukey tests have shown that the results obtained by 1H NMR and COSY methodology are similar to the obtained by the traditional GC-FID technique using external and internal standardization and normalization with 95% confidence.Item Otimização, validação e aplicação de método para determinação da concentração residual de difenoconazol em morangos após múltiplas aplicações(Química Nova, 2013-09-10) Heleno, Fernanda Fernandes; Queiroz, Maria Eliana Lopes Ribeiro de; Neves, Antônio Augusto; Oliveira, André Fernando deDifenoconazole residues in strawberry fruit cultivated in pots were estimated using the solid-liquid extraction with low temperature partition (SLE/LTP) method for sample preparation and gas chromatography with electron capture detection (GC/ECD) for analysis. The optimized method presented excellent recovery values from fortified samples and reproducibility (average recovery values ≥ 98%; CV values < 15%). Linearity of response was demonstrated (r = 0.995) with a detection limit of 9 µg kg-1. The method was successfully applied for the determination of difenoconazole residues in strawberries. Based on these results, the fungicide dissipates quickly, but the residual concentration increases after multiple applications.Item Evaluation of pesticide adsorption in gas chromatographic injector and column(Química Nova, 2012-01-31) Neves, Antônio Augusto; Pinho, Gevany Paulino de; Silvério, Flaviano Oliveira; Queiroz, Maria Eliana Lopes Ribeiro deComponents in complex matrices can cause variations in chromatographic response during analysis of pesticides by gas chromatography. These variations are related to the competition between analytes and matrix components for adsorption sites in the chromatographic system. The capacity of the pesticides chlorpyrifos and deltamethrin to be adsorbed in the injector and chromatographic column was evaluated by constructing three isotherms and changing the column heating rate to 10 and 30 ºC min-1. By using ANCOVA to compare the slope of calibration graphs, results showed that the higher the injector temperature (310 ºC) the lower the pesticide adsorption. Also, deltamethrin influenced the adsorption of chlorpyrifos on the column chromatographic.