Determination of fenoxaprop-ethyl in agricultural products by HPLC with photometric detection and mass spectrometry

Abstract

A method was developed for the determination of 6-chloro-2,3- dihydrobenzoxazol-2-one (CDHB) generated by the acid decomposition of fenoxaprop-ethyl and fenoxaprop in agricultural products. Fenoxaprop-ethyl and fenoxaprop were extracted from agricultural products using acetonitrile, and the extract was acidified by 0.5 mol/l hydrochloric acid to make CDHB. The CDHB was extracted again into ethyl acetate and cleaned up using Sep-Pak® Plus Diol and Bond Elut® AccuCAT cartridge columns. The recoveries from brown rice, wheat, cotton seed, onion, carrot, sweet potato and cabbage exceeded 70% by HPLC (UV). However, soybean, green soybeans and kidney beans showed many interference peaks in the UV spectra, and Florisil column chromatography was necessary for additional purification. The fortified peaks were confirmed by liquid chromatograph/mass spectrometry (LC/MS) with electrospray ionization (ESI), and the CDHB peak was quantitatively determined. Almost the same result was obtained by HPLC (UV) and LC/MS selected ion monitoring (SIM). Consequently, for agricultural products which included many interfering peaks during UV detection, using LC/MS (SIM) significantly improved the quantitative and qualitative analyses and the number of interfering peaks was fewer than by UV detection.