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Abstract
Hydrophobic organic compounds (HOCs) are conventionally screened by matching experimental- to reference electron ionization (EI) mass spectra acquired using gas chromatography-mass spectrometry (GC-MS). However, for identification of novel substances that are absent from EI databases, de novo structure elucidation using EI is hampered by extensive in-source fragmentation. To address this problem, a new method based on GC-atmospheric pressure chemical ionization (APCI) coupled to ion mobility-high resolution mass spectrometry (IM-HRMS) was developed for simultaneous target, suspect, and non-target screening of HOCs. Of 102 target chemicals, 85.3% produced (quasi-)molecular ions as base peaks, with 71.6% displaying method detection limits lower than those of GC-EI-low resolution MS. The optimized method was applied to standard reference sediment and sediments from the Baltic Sea, an Arctic shelf, and a Norwegian lake. In total, we quantified 56 target chemicals with concentrations ranging from 4.86 pg g-1 dwt to 124 ng g-1 dwt. Further, using a combination of exact mass, collision cross section (CCS), retention time, and MS2 spectra, a total of 54 suspects were identified at Confidence Level (CL) 2. Among the remaining features, 169 were prioritized using a halogen-selective CCS cutoff (100 Å2 + 20% mass), leading to annotation 54 substances (CL ≤3). Notably, a suite of fluorotelomer thiols, disulfides, and alkyl sulfones were identified in sediment (CL 1-2) for the first time. Overall, this work demonstrates the potential of GC-APCI-IM-HRMS as a next-generation technique for resolving complex HOC mixtures in environmental samples through exploitation of molecular ions.
Supplementary materials
Title
Supporting Information
Description
Tuning parameters (Table S1); optimization of source and tuning parameters (Section A); optimization using dieldrin for the dry condition (Figure S1); optimization for the wet condition (Figure S2); intensity fold changes using optimized and default parameters (Figure S3); sampling procedure and analysis of TOC (Section B); sampling and TOC information (Table S2); qualitative and quantitative information of target compounds (Table S3); sample preparation (Section C); instrumental method of GC-low resolution MS (Section D); software parameters (Section E); 1H NMR spectrum of 8:2/8:2 fluorotelomer disulfide (Figure S4); comparison of measured and certificated concentrations of contaminants in SRM 1941b (Figure S5); (semi)quantified concentrations of contaminants (Table S4); scores and relative intensities of suspected compounds (Table S5); qualitative information and relative intensities of non-target compounds (Table S6); representative in-source fragments of fluorotelomer thiols, disulfides, and alkyl sulfones (Figure S6).
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