Use of Quadrupole Time-of-Flight Mass Spectrometry in Environmental Analysis:  Elucidation of Transformation Products of Triazine Herbicides in Water after UV Exposure

Abstract

The high resolution and exact mass capabilities of hybrid quadrupole time-of-flight (QTOF) mass spectrometry can provide an ultimate confirmation in target analysis mode and aid in discovery and elucidation of unknown analytes. In this paper, the latter approach has been applied to study the transformation products of selected pesticides (terbuthylazine, simazine, terbutryn, terbumeton) in environmental waters. Additionally, the usefulness of software modules, originally designed for drug metabolism discovery, has been tested. Different environmental waters spiked at a 0.5 microg/mL level have been irradiated with a mercury lamp for 7 days, sampling 3-mL aliquots every approximately 12 h. After centrifugation, 50 microL was directly injected in an LC-ESI-QTOF system. The high sensitivity in full-scan mode allowed us to elucidate minor metabolites even below 2% of the total peak area. The mass errors observed in almost every case fell below 2 mDa, allowing assignment of a highly probable empirical formula. Besides, the MS/MS capability of this tandem instrument was very useful for differentiation between isomeric transformation products. This work shows that hyphenated LC-QTOF is a powerful approach for the rapid screening and confirmation of unknown pesticide transformation products in environmental water.