Identification of Trifluralin Metabolites in Soil Using Ion-Trap LC/MS/MS

摘要

Trifluralin degradation in soils is complex, potentially resulting in the formation of 28 metabolites. The objective of this research was to develop an approach for the identification of trifluralin metabolites in soils using ion-trap liquid chromatography/mass spectrometry (LC/MS/MS). Authentic standards of the parent and six metabolites were used to establish appropriate instrument conditions and precursor ion (PI) fragmentation patterns to confirm their identity, as well as to facilitate confirmation of metabolites for which authentic standards were not available. Two soils from herbicide spill sites known to be contaminated with trifluralin were selected for study because of their high potential for metabolite detection. Soils were extracted with 70% aqueous acetonitrile, filtered, and directly injected into the ion-trap LC/MS/MS. Trifluralin metabolites were then identified as follows: 1) screen for PI masses; 2) compare retention time of the PI peak to standards; and 3) obtain PI spectra and compare fragmentation with standards. The validity of this approach was confirmed for the identification of metabolite, TR-20. Preliminary results identified the presence of up to eight metabolites in the soils, and the array of metabolites present were indicative of aerobic trifluralin degradation.