Compositional space: A guide for environmental chemists on the identification of persistent and bioaccumulative organics using mass spectrometry

• Published in: Environment international 2019-11, Vol.132, p.104808-104808, Article 104808
• Main Authors: Zhang, Xianming, Di Lorenzo, Robert A., Helm, Paul A., Reiner, Eric J., Howard, Philip H., Muir, Derek C.G., Sled, John G., Jobst, Karl J.
• Format: Article
• Language: English
• Subjects: Air Pollution, Indoor; Chemical space; Dust - analysis; Environmental mass spectrometry; Environmental Monitoring; Environmental Pollutants - analysis; Flame retardants; Flame Retardants - analysis; Halogenation; Humans; Mass Spectrometry; Nontargeted screening; Persistent organic pollutants
• ISSN: 0160-4120; 1873-6750
• DOI: 10.1016/j.envint.2019.05.002

Since 2001, twenty-eight halogenated groups of persistent organic pollutants (POPs) have been banned or restricted by the Stockholm Convention. Identifying new POPs among the hundreds of thousands of anthropogenic chemicals is a major challenge that is increasingly being met by state-of-the-art mass spectrometry (MS). The first step to identification of a contaminant molecule (M) is the determination of the type and number of its constituent elements, viz. its elemental composition, from mass-to-charge (m/z) measurements and ratios of isotopic peaks (M + 1, M + 2 etc.). Not every combination of elements is possible. Boundaries exist in compositional space that divides feasible and improbable compositions as well as different chemical classes. This study explores the compositional space boundaries of persistent and bioaccumulative organics. A set of ~305,134 compounds (PubChem) was used to visualize the compositional space occupied by F, Cl, and Br compounds, as defined by m/z and isotope ratios. Persistent bioaccumulative organics, identified by in silico screening of 22,049 commercial chemicals, reside in more constrained regions characterized by a higher degree of halogenation. In contrast, boundaries surrounding non-halogenated chemicals could not be defined. Finally, a script tool (R code) was developed to select potential POPs from high resolution MS data. When applied to household dust (SRM 2585), this approach resulted in the discovery of previously unknown chlorofluoro flame retardants. [Display omitted] •Elemental composition determination is the first step to identifying a contaminant.•Boundaries in compositional space enclose persistent organic pollutants (POPs).•~305,134 compounds (PubChem) were used to visualize the space occupied POPs.•A script tool was developed to select potential POPs from high resolution MS data.•Unknown Cl/F-flame retardants were identified in house dust.