Gas Chromatography/Electron Ionization-Mass Spectrometry-Selected Ion Monitoring Screening Method for a Thorough Investigation of Polyhalogenated Compounds in Passive Sampler Extracts with Quadrupole Systems

摘要

Nontarget analysis and identification of unknown polyhalogenatedncompounds is important in acquiring a thoroughnpicture of the present pollution status as well as fornidentifying emerging environmental problems. Such analysesnusually require the application of electron ionizationnmass spectrometry because the resulting mass spectranfrequently allow for compound identification. When quadrupolesnare used as mass separators, the full scanntechnique often suffers from low sensitivity along withnnonspecificity for polyhalogenated trace compounds whichnoften result in interference by matrix compounds. We havendeveloped a novel nontarget gas chromatography/electronnionization-mass spectrometry-selected ion monitoring (GCEI-MS-SIM) method that overcomes these sensitivity andnselectivity issues. Our method is based on the fact thatnthe molecular ions and isotope patterns of polyhalogenatedncompounds involve the most relevant primaryninformation with regard to the structure of polyhalogenatedncompounds. Additionally, the retention times ofnpolyhalogenated compounds generally increase with increasingnmolecular weight. The retention time range ofnpolyhalogenated compounds was divided in three partlynoverlapping segments of 112 u (segment A:m/z 300-412;nsegment B: m/z 350-462; segment C: m/z 450-562)nthat were screened in eight GC runs consisting of 15nconsecutive SIM ions. This method was tested with anpassive water sampler extract known to contain over 30npolyhalogenated compounds according to the sensitivenanalysis by GC/electron capture negative ion (ECNI)-MS.nWhile none of these polyhalogenated compounds couldnbe detected by GC/EI-MS in full scan mode, our nontargetnGC/EI-MS-SIM method allowed for the detection of 38npolyhalogenated compounds. Only seven could be identifiednby means of reference standards while more than 15nof the unknowns could be traced back to at least the classnof compounds based on the mass spectrometric data fromnthe nontarget SIM runs. All compounds identified originatednfrom halogenated natural products. The nontargetnGC/EI-MS-SIM method combines the high sensitivitynobtainable with quadrupole systems for trace analysis withnthe structural information essential for the identificationnof unknown pollutants.