Analytical Method of Phoxim in Agricultural Products by GC-FPD and GC/MS (SIM)

Abstract

An analytical method for residual analysis of phoxim in agricultural products by gas chromatography-flame photometric detection (GC-FPD) and gas chromatography-mass spectrometry (GC/MS) using selected ion monitoring (SIM) was established. Since phoxim was unstable during GC measurement, the effect of injection port and column temperatures on the response was studied, and an appropriate injection port temperature (150-190°C) and column temperature (150°C) were selected.Phoxim was extracted from agricultural products with acetone, diluted with saturated NaCl solution, and re-extracted with ethyl acetate. The extract was defatted by acetonitrile-n-hexane partitioning for grains. When an interfering peak was observed, the extract was cleaned up by using Sep-pak® Silica cartridge column chromatography. Recoveries of phoxim in 6 kinds of agricultural products spiked with phoxim at the maximum residue limit (0.05-0.2ppm) were 75.3-95.1% by GC-FPD and 79.4-95.0% by GC/MS (SIM). A good agreement of quantification results was observed between the GC-FPD and GC/MS (SIM) methods.The mass spectrum of phoxim in agricultural products at the low levels used in the recovery test could not be measured. Therefore, phoxim was confirmed by using the relative abundance ratios of fragment ions determined by GC/MS (SIM). Using these relative abundance ratios and retention time data, phoxim could be confirmed from ca. 70 pesticides which could be measured directly by GC.