Otimização e validação de metodologia para determinação de aldicarbe e carbofurano em amostras de café bebida

• Autor(a) principal: Alves, Renata Domingos
• 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/123456789/2090
• topic: Análise de resíduos; Carbamatos; Partição em baixa temperatura; Residue analysis; Carbamates; Low temperature partitioning; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ANALITICA

Domestic use of aldicarb and carbofuran has resulted in accidental or even intentional poisonings, making it a severe public health problem. A mixture of "chumbinho" (aldicarb) in coffee is frequently a poisoning agent due to strong odor and color of coffee which hide the presende of "chumbinho". Thus, the objective of this study was to adapt, optimize and validate a liquid-liquid extraction technique with low temperature partitioning (LLE-LTP) for determination of aldicarb and carbofuran in coffee by high performance liquid chromatography (HPLC-UV), aiming to make the technique available for poisoning cases of forensic and agrarian interest. Preliminary tests were performed on optimization of the method for the evaluation of variables from extraction of pesticides such as: solvent extractor, volume of the sample and solvent extractor, pH of the sample, ionic force, homogenization mode and times of agitation, fortification and partitioning. Later, a complete 22 factorial scheme was used for evaluation of the simultaneous behavior of NaCl concentration in the sample (0% or 3% w/v) and pH of the sample (3.0 or 5.5) on extraction efficiency of the carbamates. The optimized method consisted of adding 2.0 mL of the coffee sample (8% w/v) and 4.0 mL of acetonitrile, verifying the formation of a single phase. This mixture is then agitated on a table agitator (5 minutes) and placed in a freezer at -20°C for 3 hours. Under these conditions the phases are separated and the organic extract which contains the active principles which is recovered and analyzed by HPLC, employing water and acetonitrile as the mobile phase (65:35). The optimized technique was validated, determining the principle figures of merit, including: selectivity, detection and quantification limits and linearity. Effect of the matrix on quantification of these active principles by HPLC was also evaluated. The results indicated that the LLE-LTP method is efficient for extraction of the two pesticides in coffee samples, showing recovery percentages greater than 94%. Detection and quantification limits of the method were 0.54 and 1.80 mg L-1 respectively for aldicarb and 0.28 and 0.92 mg L-1 for carbofuran. The effect of the matrix showed to be present on quantification of the pesticides by liquid chromatography. In the study of the stability of these active principles, it was observed that of the three factors analyzed, storage temperature of the samples was the factor that most affected degradation of the carbamates. At room temperature, fungi growth as wellas greater degradation of the composts was observed after 5 days. Therefore, optimization of the LLE-LTP method for extraction of pesticide residues from coffee samples and analysis by HPLC resulted in a simple and effective method, with little consumption of solvent, high analytical frequency and low cost.