Simultaneous determination of fipronil and its major metabolites in corn and soil by ultra-performance liquid chromatography-tandem mass spectrometry

A simple, quick, effective method was developed for the determination of fipronil and its three metabolites in soil and corn by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Samples were extracted with acetonitrile and cleaned-up with C18, C18/PSA, PSA/GCB for soil, corn grain, and corn straw, respectively. The optimization of MS/MS parameters was performed in multi-reaction monitoring (MRM) mode, and electrospray ionization (ESI) in the negative mode was selected. The mean recoveries of the four compounds in soil, corn grain, and corn straw matrices at four fortification levels were in the range of 82.4% to 104.6%; the intra-day and inter-day RSDs ranged from 1.2% to 7.7% and 2.4% to 9.4%, respectively. The LODs of fipronil and its three metabolites in soil, corn grain, and corn straw matrices were estimated to be 0.5-2.5 mu g kg(-1), the LOQs were 5 mu g kg(-1) for soil and corn grain, and 10 mu g kg(-1) for corn straw. The developed method was also applied to the study of fipronil dissipation in soil and corn. The results further confirmed the reliability and efficacy of the proposed method for routine pesticide residue monitoring in soil and corn samples.