Rapid Multiresidue Method for the Determination of more than 300 Pesticide Residues in Food

The aim of this study was to develop a simple and efficient sample preparation methodology in pesticide multiresidue analysis that shortens the analytical process during extraction and cleanup. We have conducted recovery tests of about 300 pesticides in foods with a modified method reported previously. Ten g of sample was extracted with 20 ml of acetonitrile using a high-speed homogenizer. One gram of NaCl and 4 g of anhydrous MgSO4 were added and shaken immediately. The tube was centrifuged to separate the sediment and water from the acetonitrile extract. The acetonitrile layer obtained after salting out was loaded into the double-layered SPE cartridge with a graphitized carbon black and primary secondary amine, followed by elution with acetonitrile-toluene (3:1). The eluate was evaporated and the residue was dissolved in acetone-hexane (1:9) or methanol. The test solution was determined by a GC-FPD for organophosphorous pesticides, GC-MS in the NCI mode for organochlorines, pyrethroids and other halogenated pesticides, and GC-MS in the EI mode for other pesticides. LC-MS/MS was also used to determine less volatile pesticides. Recovery studies were performed by fortifying 3 or 5 matrices at 0.05 or 0.1 μg/g. Recoveries of about 300 pesticides were mainly 70-110% and the relative standard deviations were below 20%. Limits of detection ranged between 0.1 and 50 ng/g for tested pesticides. _____________________________________________________________________________________________________________