Nontarget GC-ECNI-Orbitrap-HRMS screening and evaluation method used to identify polyhalogenated compounds extracted from two passive air samplers deployed at marine islands in Australia

Gas chromatography with electron capture negative ion high resolution mass spectrometry (GC-ECNI-Orbitrap-HRMS) was applied for the comprehensive analysis of halogenated natural products (HNPs) and anthropogenic organohalogen compounds in two passive air samples from Australian marine islands. This enabled the detection of ~250 halogenated compounds in the two air samples of which reference standards were available for only ten. For the evaluation, the compounds were listed according to the exact mass of the nonhalogenated backbone (halogens in the molecular formula were replaced with hydrogens; primary list) calculated in the next step. This meant that compounds with the same backbone were listed together, which was crucial for data interpretation. Specifically, the ~250 compounds could be traced back to ~100 different backbones. Four additionally calculated secondary lists allowed to indicate structurally related homologues if their exact masses were also found in the primary list. Key-findings include the detection of several sponge-derived HNPs and > 20 halogenated nitrobenzenes and nitrophenols, including iodine-containing ones. The primary and secondary list-based evaluation turned out to be a promising approach for other complex data sets with polyhalogenated compounds. • Nontarget GC-ECNI-Orbitrap-HRMS screening of two Australian air samples. • Characterization of many of the ~250 organohalogen compounds detected. • Replacement of halogens in the molecular formula with hydrogens. • Data evaluation strategy based on the backbones of the compounds.