Otimização e validação da técnica de extração líquido - líquido com partição induzida por sal para análise de agrotóxicos em amostras de água por cromatografia gasosa e aplicações

• Autor(a) principal: Rodrigues, Alessandra Aparecida Zinato
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2092
• topic: Agrotóxico; Água; Cromatografia gasosa; Pesticides; Water; Gas chromatography; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ANALITICA

In the stage of optimizing the liquid-liquid extraction with salt induced partitioning technique (LLE-SIP) for analysis of pesticides in water, preliminary tests were performed to evaluate the best conditions for their extraction and analysis. Later, the best responses were used as reference for a 23 experimental planning to evaluate the simultaneous behavior of the following factors: sample proportion, solvent extractor, saline concentration and form of agitation. To a single phase mixture composed of water and solvent extract, 1.0 mL of a saline solution (NaCl) was added to separate the phases. The mixtures were agitated, left in repose, and the upper organic phase containing the pesticides of interested was separated, followed by addition of an internal standard and volume adjustment. The optimized LLE-SIP method was validated for some figures of merit: selectivity, linearity, detection and quantification limits of the device and method, precision and accuracy. The limits of detection (LOD) and quantification (LOQ) of the method were 0.15 and 0.5 µg L-1 for chlorpyrifos, 5.5 and 18.2 µg L-1 for thiamethoxam, 1.5 and 5.0 µg L-1 for cypermethrin and 3.7 and 12.0 µg L-1 for deltamethrin, respectively. The rate of recovery obtained for the proposed method varied from 75 to 90%, with relative standard deviation less than 10%. Coefficients of determination (r2) for the analytical curves of the four pesticides were greater than 0.99 in the utilized concentration range. The LLE-SIP method, after validation, was applied to water samples, not detecting the presence of any of the four pesticides in these samples. The methods of extraction and analysis were also applied to water samples from washing of fruits and vegetables (strawberry, apple, tomato and green pepper) as well as their pulps. Residues of the active principle thiamethoxam were encountered both in the water as well as the pulp of strawberry, apple, green pepper and tomato, in values greater than the maximal residue levels established by the ANVISA. Cypermethrin and chlorpyrifos were also detected in strawberries and bifenthrin was detected in apples, despite these substances not being permitted for these specific crops. The results presented in this stage of work showed that conventional washing of a food with water does not completely reduce the residual levels of pesticides present in fruits and vegetables.