Expanding Atmospheric Surveillance: Non-Target Screening and Open Spectral Databases for Persistent Halogenated Compounds

The Montreal Protocol (1989) is widely regarded as one of the most successful environmental agreements, having phased down ozone-depleting substances such as chlorofluorocarbons (CFCs), followed by hydrofluorocarbons (HCFCs) in 2013 and hydrofluorocarbons (HFCs) in 2019. Today, developed countries primarily use hydrofluoroolefins (HFOs) as fourth-generation replacements. A key factor in this success is continuous global monitoring of these compounds. The Scientific Assessment of Ozone Depletion, published every four years, lists over 780 substances with their ozone-depleting potential (ODP) and global warming potential (GWP). However, fewer than 10% (~70) have quantified atmospheric abundances, primarily measured by the Ad-vanced Global Atmospheric Gases Experiment (AGAGE) network using cryogenic pre-concentration (Medusa) coupled with gas chromatography quadrupole mass spectrometry (GC–qMS).
As the number of regulated and unregulated compounds grows, comprehensive detection is essential. Quadrupole MS limits ion coverage, prompting the development of a non-target screening (NTS) approach. We combine an advanced preconcentration unit (Aprecon), GC-time-of-flight MS, and the ALPINAC algorithm for automated fragment formula annotation. This workflow has identified more than 80 previously unidentified persistent halogenated compounds in routine air samples.
To support global research efforts, we provide a suspect screening list of atmospheric compounds of concern, including mass fragments and retention time indices. High-resolution mass spectra are shared via Mass Bank, including data for compounds lacking publicly available spectra. This resource enhances the identification and monitoring of emerging halogenated substances, strengthening global capacity to track and mitigate their environmental impact.