Gas Phase Reactivity of Isomeric Hydroxylated Polychlorinated Biphenyls

Emma H Palm; Josefin Engelhardt; Sofja Tshepelevitsh; Jana Weiss; Anneli Kruve

doi:10.1021/jasms.4c00035

Gas Phase Reactivity of Isomeric Hydroxylated Polychlorinated Biphenyls

J Am Soc Mass Spectrom. 2024 May 1;35(5):1021-1029. doi: 10.1021/jasms.4c00035. Epub 2024 Apr 19.

Authors

Emma H Palm^{1

2}, Josefin Engelhardt³, Sofja Tshepelevitsh⁴, Jana Weiss³, Anneli Kruve^{1

3}

Affiliations

¹ Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16, 114 18 Stockholm, Sweden.
² Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, 6 avenue du Swing, 4367 Belvaux, Luxembourg.
³ Department of Environmental Science, Stockholm University, Svante Arrhenius väg 8, 114 18 Stockholm, Sweden.
⁴ Institute of Chemistry, University of Tartu, Ravila 14a, 50411, Tartu, Estonia.

PMID: 38640444
DOI: 10.1021/jasms.4c00035

Abstract

Identification of stereo- and positional isomers detected with high-resolution mass spectrometry (HRMS) is often challenging due to near-identical fragmentation spectra (MS²), similar retention times, and collision cross-section values (CCS). Here we address this challenge on the example of hydroxylated polychlorinated biphenyls (OH-PCBs) with the aim to (1) distinguish between isomers of OH-PCBs using two-dimensional ion mobility spectrometry (2D-IMS) and (2) investigate the structure of the fragments of OH-PCBs and their fragmentation mechanisms by ion mobility spectrometry coupled to high-resolution mass spectrometry (IMS-HRMS). The MS² spectra as well as CCS values of the deprotonated molecule and fragment ions were measured for 18 OH-PCBs using flow injections coupled to a cyclic IMS-HRMS. The MS² spectra as well as the CCS values of the parent and fragment ions were similar between parent compound isomers; however, ion mobility separation of the fragment ions is hinting at the formation of isomeric fragments. Different parent compound isomers also yielded different numbers of isomeric fragment mobilogram peaks giving new insights into the fragmentation of these compounds and indicating new possibilities for identification. For spectral interpretation, Gibbs free energies and CCS values for the fragment ions of 4'-OH-CB35, 4'-OH-CB79, 2-OH-CB77 and 4-OH-CB107 were calculated and enabled assignment of structures to the isomeric mobilogram peaks of [M-H-HCl]^- fragments. Finally, further fragmentation of the isomeric fragments revealed different fragmentation pathways depending on the isomeric fragment ions.