Application of inert gas-mediated ionization for qualitative screening of chlorinated aromatics in house dust by comprehensive two-dimensional gas chromatography-high-resolution time-of-flight mass spectrometry

Utilization of Negative Chemical Ionization to Expand Nontargeted Screening of Halogenated Organics in Great Lakes Top Predator Fish

Nontargeted screening (NTS) of halogenated contaminants in biota is part of the routine monitoring of the Great Lakes ecosystem. NTS can give insight into new chemicals with possible persistent, bioaccumulative, and toxic (PBT) properties and help quantify known PBT's degradation and transformation products. The most common ionization technique for NTS is electron impact ionization (EI) due to the consistent and easily standardized fragmentation patterns. This research uses electron capture negative ionization (ECNI) as a complementary technique to broaden the range of halogenated contaminants detected in the Great Lakes. ECNI has higher sensitivity and selectivity to halogenated compounds compared to EI. GC × GC-HR-ToF MS with a multimode ion source (MMS) offers consecutive runs in EI and ECNI modes using the same chromatographic setup, facilitating retention time alignment. The exact mass measurements help in identifying compounds found only in ECNI. A total of 85 novel halogenated features were detected, 78% of which were detected only in ECNI. Only 9% of the features were detected in both modes, indicating that ECNI is a necessary complementary technique for NTS of halogenated features.

Comprehensive characterization and prioritization of halogenated organic compounds in fish and their implications for exposure

Fish are an important pollution indicator for biomonitoring of halogenated organic compounds (HOCs) in aquatic environments, and HOCs in fish may pose health threats to consumers. This study performed nontarget and comprehensive analyses of HOCs in fish from an e-waste recycling zone by gas chromatography-high-resolution mass spectrometry, and further prioritized their human exposure risks. A total of 1652 formulas of HOCs were found in the fish, of which 1222, 117, and 313 were organochlorines, organobromines, and organochlorine-bromines, respectively. The total concentrations of HOCs were 15.4-18.7 μg/g (wet weight), and organobromines were the predominant (14.1-16.8 μg/g). Of the HOCs, 41 % were elucidated with tentative structures and divided into 13 groups. The estimated total daily exposures of HOCs via dietary consumption of the fish for local adult residents were 3082-3744 ng/kg bw/day. The total exposures were dominated by several groups of HOCs with the following contribution order: polyhalogenated biphenyls and their derivatives > polyhalogenated diphenyl ethers > halo- (H-)alkanes/olefines > H-benzenes > H-dioxins > H-polycyclic aromatic hydrocarbons > H-phenols. The comprehensive characterization and prioritization results provide an overview of the species and distributions of HOCs in edible fish, and propose an inventory of crucial HOCs associated with high exposure risks.