Otimização, comparação e validação de métodos de extração e quantificação de pesticidas e HPAs em cachaça

Abstract

This work aims at analyzing the development and validation of two multiresidue methods: one to determine 95 pesticides and another to determine 16 polycyclic aromatic hydrocarbons, both in cachaça, using a sole liquid-liquid extraction procedure with the addition of salts. The analytes were separated, identified and quantified by means of GC-MS/MS, in select reaction monitoring mode. Three extractions and clean-up procedures were optimized and compared as to recovery and repeatability: liquid-liquid extraction, solid phase extraction and liquid-liquid extraction with salt addition. The liquid-liquid extraction, at optimized condition, consisted of evaporation of 40% of the sample volume and the use of dichloromethane as solvent extractor. The solid phase extraction, at optimized condition, consisted of: evaporation of 40% of sample volume, cleaning of the cartridge with 5 mL of ultrapure water and elution of the analytes with 10 mL of dichloromethane. The liquid-liquid extraction with salt addition was optimized with 10 mL of dichloromethane. The last procedure was evaluated as the most adequate for extraction and clean-up of the analytes studied and validated according to criteria recommended by monitoring agencies. The validation parameters evaluated showed good performance of both methods, with adequate linearities, and tr calculated was greater than the critical value, at confidence level of 95%. Pesticides: trueness with recoveries between 81113%; variation coefficient 20%, for at least two fortification levels, except for lambda cyhalothrin and methamidophos; detection and quantification limits, 0.0025 and 0.01mg L-1, respectively. PAHs: trueness with recoveries between 84.76120.78%; variation coefficient between 6.2327.33%; detection and quantification limits, 0.00025 and 0.001 mg L-1, respectively. Measurement uncertainty was verified and presented good results, mainly at higher relevant analytical levels. Twenty-six samples were analyzed: commercial cachaça samples and head, heart and tail to distillation fractions of two stilleries. The results showed contamination by 31 pesticides and 12 different PAHs, with fenbuconazole (present in 10 samples) and benzo(a)pyrene (present in 19 samples), the most present representative of each category of contaminants.