Multiresidue Determination of Pesticides in Fruits and Vegetables by Gas Chromatography/Mass Spectrometry/Selected Ion Monitoring

CHUN-LUNG CHENG, SHUR-JYUAN SHIH, *GOW-CHIN YEN, SHIN-SHOU CHOU AND CHAO-HONG LIU

National Laboratories of Foods and Drugs, Department of Health, Executive Yuan
*Department of Food Science, National Chung-Hsing University, Taichung

ABSTRACT

   A multiresidue method using gas chromatography/mass spectrometry/selected ion monitoring (GC/MS/SIM) for the determination of captan, chlorothalonil, cyanofenphos, dichlorvos, dimethoate, EPN, fonofos, mevinphos, phenthoate, phorate, pirimiphos-methyl, and prothiophos residues in fruits and vegetables was evaluated. The pesticides were extracted with a slightly modified Luke multiresidue procedure, separated by capillary column gas chromatography, and detected by mass chromatography with a quadrupole mass spectrometer in the electron impact mode. Recovery studies were performed at the 0.5 ppm fortification level of each pesticide in apples, cabbages, cucumbers, grapes and pak-choi. Recoveries were between 46 and 108%. Coefficients of variation were between 0.7 and 19.0%, with an average of 7.5%. The estimated limits of detection of the pesticides in the crops were 0.1-0.05 ppm, except that captan had limits of detection in the crops higher than 0.5 ppm. Because the mass spectrometer is capable of achieving higher levels of molecular specificity as compared to the traditional GC detectors and can be programmed to search for several hundred target inos, GC/MS would be a promising method for regulatory agencies to explore for monitoring pesticide residues in daily food supply.

Key words : Pesticides, Residues, Multiresidue method (MRM), GC/MS/SIM