Análise multirresíduos de agrotóxicos em alface por cromatografia gasosa

• Autor(a) principal: Costa, Anna Isabel Guido
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2099
• topic: Análise multirresíduos; Agrotóxicos; Alface; Cromatografia gasosa; Multiresidue analysis; Pesticides; Gas chromatography; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ANALITICA

Lettuce (Lactuca sativa L.) is one of the most fresh salad consumed by all social classes in Brazil. It is very important for food security, the monitoring and evaluation of all aspects related to production and consumption. In this study, was optimized and validated a methodology for determining, in samples of lettuce, the residues of eleven pesticides (chlorothalonil, parathion-methyl, chlorpyrifos, thiamethoxam, procymidone, endosulfan, iprodione, lambdacyhalothrin, permethrin, cypermethrin and deltamethrin). Using the method of SLE-LTP and analysis by Gas Chromatography with Electron Capture Detector (GC ECD). In the optimization of univariate method were assessed parameters that could influence the extraction of pesticides as adding water, organic solvent, time and mode of stirring, effect of pH, ionic strength, freezing and centrifugation times, volume of organic solvent and sample mass. The optimized method consists of adding to 4.0000 g of lettuce, 1.0 mL of water, 6.5 mL of acetonitrile and 1.5 mL of ethyl acetate and checking the formation of one single phase. This mixture is agitated on a shaker (10 min.), centrifuged for 3 minutes at 1200 g and taken to a freezer at -20 oC for 3 hours. Under these conditions the phases are separated and the organic extract containing the active ingredient is passed through a filter paper containing anhydrous sodium sulfate. This extract is recovered and analyzed GC-ECD. The optimized technique was validated by determining the main figures of merit such as selectivity, linearity, limits of detection and quantification, accuracy and precision. Was evaluated the matrix effect on quantification of active principles by GC-ECD. The results indicates that SLE-LTP is an efficient method for the extraction of the eleven pesticides in samples of lettuce, showing recovery percentages greater than 57.0% and less 103.0%. The limits of detection and quantification were 0.0004 to 0.0520 mg.kg-1 and from 0.0012 to 0.1716 mg.kgxviii 1, respectively. The matrix effect was present in the quantification of pesticides by gas chromatography. The optimized and validated technique was applied to the analysis of residues of chlorothalonil, thiamethoxan, procymidone and iprodione in lettuce, which were sprayed in an experimental garden in accord with good agricultural practices, respecting the security space of each product. In the study of the stability in the solvent, was observed that analytes such as permethrine and procymidone are quite stable, even when stored in freezer or exposed to the environment. The other compounds showed more instability behavior. The other compounds in the matrix-extract, it is concluded that coextractives degradation during the period of spectrophotometric monitoring did not influence the stability of analytes in solution. Thus, the optimization of SPELTP technique and analysis by CG-ECD samples of lettuce for the extraction pesticides residues resulted in a simple, effective, whit a little solvent consumption and low cost method.