Development, Validation and Application of a Methodology Based on Solid-phase Micro Extraction Followed by Gas Chromatography Coupled to Mass Spectrometry (SPME/GC-MS) for the Determination of Pesticide Residues in Mangoes

A method was developed for the simultaneous analysis of 14 pesticide residues (clofentezine, carbofuran, diazinon, methyl parathion, malathion, fenthion, thiabendazole, imazalil, bifenthrin, permethrin, prochloraz, pyraclostrobin, difenoconazole and azoxystrobin) in mango fruit, based on solid-phase micro extraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS). Different parameters of the method were evaluated, such as fiber type, extraction mode (direct immersion and headspace), temperature, extraction and desorption times, stirring velocities and ionic strength. The best results were obtained using polyacrylate fiber and direct immersion mode at 50 degrees C for 30 min, along with stirring at 250 rpm and desorption for 5 min at 280 degrees C. The method was validated using mango samples spiked with pesticides at concentration levels ranging from 33.3 to 333.3 microg kg(-1). The average recoveries (n=3) for the lowest concentration level ranged from 71.6 to 117.5%, with relative standard deviations between 3.1 and 12.3%, respectively. Detection and quantification limits ranged from 1.0 to 3.3 microg kg(-1) and from 3.33 to 33.33 microg kg(-1), respectively. The optimized method was then applied to 16 locally purchased mango samples, all of them containing the pesticides bifenthrin and azoxystrobin in concentrations of 18.3-57.4 and 12.7-55.8 microg kg(-1), respectively, although these values were below the MRL established by Brazilian legislation. The method proved to be selective, sensitive, and with good precision and recovery rates, presenting LOQ below the MRL admitted by Brazilian legislation.