Estudo de método multirresíduo para determinação de agrotóxicos em águas superficiais por SPE e GC-MS/MS

Abstract

Modern agriculture started using different techniques and materials in order to minimize losses in production and meet the growing demand for food, combining productivity and profitability. However, the indiscriminate use of these different inputs (pesticides and fertilizers) can lead to several environmental damage. Study conducted by the National Agency for Sanitary Vigilance regarding the pesticide market in Brazil reveals that there pace of expansion in consumption, putting the country on alert in conferring the enhancement of environmental contamination arising from the use of pesticides. The present work aims to study multiresidue method for determination of pesticides using solid phase extraction and quantification by gas chromatography coupled to mass spectrometry in tandem GC-(TQ) -MS/MS, as well as evaluating the storage of compounds directly extraction cartridges in different time periods. To optimize the extraction procedure was used factorial planning, assessing three kinds of sorbents, Oasis ® HLB, C18 Strata Strata-X ® and varying proportions of methanol in methylene chloride as well as different pH values. The extraction procedure is optimized for use with the sorbent cartridge SPE Oasis ® HLB polymeric mg/3mL 60, the sample filtered with 0.22 nylon membrane micrometers. Conditioning the cartridge with 3 mL of methanol followed by 3 mL of ultrapure water and 3 ml of ultrapure water at pH (6.2). Percolation 100 mL sample previously acidified to pH 6.2. For elution was used a mixture of MeOH: DCM 45:55 (v, v) with two additions of 1 mL, leaving two minutes of contact with the sorbent before elution. The assessment of figures of merit for the proposed method were satisfactory, with linear calibration curves with r2 greater than 0.99 in the range 5-200 mg L-1, with values of LODm LOQm and 0.03 and 0.10 mg L-1, respectively. When evaluated recoveries found values between 70 and 120% for 39 of the 43 pesticides evaluated with precision values RSD ≤ 20%. The matrix effect was evaluated and proved to be over 10% for most compounds. The application of the method was performed on 10 samples of dams in different cities of Colonial Northwest region of Rio Grande do Sul, found pesticide residues in eight. The method proved to be effective for the determination of pesticide residues by SPE and GC-(TQ) -MS/MS, being able to be used in routine analysis.