The Impact of Pesticides - Academy Publish

solvent is commonly used to extract the analytes of interest. These steps of the SPEmethod depend on the physic chemical properties of the pesticides and theirconcentrations, so as to utilize the ideal volume of solvent.Single-drop microextraction (SDME)is a simple and inexpensive extractiontechnique that involves the consumption of small quantities of the solvent.Thistechnique consists of the addition of a small drop (8.0µL)of the organic solvent(noctane)to the aqueous sample containing the analyte. The solution is agitated for ashort period (approximately 5 min)at constant velocity.Then,an aliquot of 1.0 µL ofthe organic phase is injected in the chromatograph for analysis (Jeannot andCantwell 1996).Solid phase microextraction (SPME) is a technique for sample treatment publishedin 1989 by Pawliszyn and Belardi (Zhang, Yang et al. 1994), applied in theextraction of organic compounds indifferent matrices, such as air, water, soil andfood. The SPME technique is promising and has the advantage of not using solventsfor extraction. It basically consists of partitioning compounds between the sampleand the stationary phase (fiber of fused silica covered with polymeric film andadapted to a syringe) followed by thermal desorption of these compounds in ananalytical instrument for qualitative and quantitative determination (Cardeal, Rabeloet al. 1999).Other extraction methods have been used in order to develop multiresidue methodsfor determination of pesticides in food. Among these, highlighted is the methoddeveloped in 2003 by Anastassiades et al. (Lehotay, Michelangelo et al. 2010),referred to as QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe). Thismethod involves initial extraction with a solvent such as acetonitrile, followed by aliquid-liquid partition.It comprises the addition of some salts (responsible for theseparation of the aqueous phase from the organic phase and removal of significantamounts of polar compounds in the matrix) and buffering agents (for protection ofanalytes susceptible to degradation in alkaline or acidic conditions). The extractobtained is subjected to an extraction process in dispersive solid phase for “cleanup”. The sorbent used varies in function of the matrix nature. This method requires asmall sample size, consumes small amounts of solvent, produces satisfactory resultsin terms of accuracy and repeatability, allows the preparation of a considerablenumber of samples in a short time and is suitable for analyzing a wide range ofpesticides by both gas chromatography and high performance liquidchromatography.Analytical Determinations of Pesticides in CoffeeSeveral analytical methods were developed for identification and quantification ofpesticides in food and the environment. Among the main analytical techniques usedare gas chromatography (GC) equipped with an electron capture detector (ECD) ornitrogen and phosphorus detector (NPD) or mass spectrometry (MS) detector andhigh performance liquid chromatography (HPLC) using UV or MS detection, sincethese methods possess the selectivity, sensitivity and high capacity necessary foridentification and quantification of pesticides.Yang et al. (2011) developed a multiresidue method for determination of 69pesticides (2,6-dinitroaniline, amide, azole, carbamate, chloroacetamide, diphenylether, organochlorine, organophosphates thio and dithiocarbamates, triazine andtriazole)in coffee beans by GC/MS. The sample preparation used SPE techniqueswith Envi-carb cartridges, and gel permeation chromatography (GPC) with ethylacetate-n-hexane as mobile phase. The method showed good linearity withcorrelation coefficients (R 2 ) above 0.99. Recovery in samples spikedwith 0.05 to1.00 µg kg -1 presented values between 60-120%. The precision (RSD) was betweenAcademyPublish.org - The Impact of Pesticides383