Development of Residue Analysis for Pesticides by LC/MS and LC/MS/MS Methods

Some agricultural chemicals having high polarity, low vapor pressures or high thermal instability are not directly amenable to GC and GC/MS. We established new analytical methods using LC/MS and LC/MS/MS for such agricultural chemicals as pyrethroids, neonicotinoids and guanidines. The analytical method of a pyrethroid insecticide, tralomethrin, using gas chromatography (GC) with electron-capture and mass spectrometry (MS) detectors is to measure the deltamethrin transformed from tralomethrin in the injector port of the GC system. By using LC/MS, however, both pesticides could be separated and determined simultaneously. Although gas chromatography (GC) and high-pressure liquid chromatography with fluorescence (HPLC-FL) have been used for guanidino pesticides determination, a derivatization step is usually required. Moreover, guanidino pesticides that easily adsorb sample matrixes could also be analyzed by using LC/MS without a derivatization step. In the case of nitenpyram, a neonicotinoid pesticide, its metabolites have been determined by GC after derivatization. However, ten compounds including the metabolites could be simultaneously and selectively analyzed by using LC/MS/MS. In addition, the effect of additives on the extraction efficiency, an important factor for the analytical method, could be outlined.