Evidence of complementarity between targeted and non-targeted analysis based on liquid and gas-phase chromatography coupled to mass spectrometry for screening halogenated persistent organic pollutants in environmental matrices

This study explored the complementarity between targeted (TS) and non-targeted screening (NTS) based on liquid and gas-phase chromatography coupled to (high-resolution) mass spectrometry (LC-/GC-(HR)MS) for the comprehensive characterization of organohalogen fingerprints within a set of Lake Ontario lake trout samples. The concentrations of 86 legacy, emerging and novel halogenated compounds (HCs), were determined through 4 TS approaches involving no less than 6 hyphenated systems. In parallel, an innovative NTS strategy, involving both LC and GC-Q-Orbitrap, was implemented to specifically highlight halogenated signals. Non-targeted HRMS data were processed under the HaloSeeker software based on Cl and Br isotopic ratio and mass defect to extend the screening to unsuspected and unknown HCs. A total of 195 halogenated mass spectral features were characterized in the Lake Ontario lake trout, including well known HCs (PCBs, PBDEs, PBBs, DDT and their degradation products), emerging HCs (novel brominated flame retardants, short-, medium- and long-chain chlorinated paraffins) or suggested molecular formula (mainly polychlorinated ones). Among the 122 HCs highlighted by TS, only 21 were identified by NTS. These results fueled a discussion on the potential and limitations of both approaches, and the current position of NTS within environmental and health monitoring programs.