Ion mobility mass spectrometry for suspect screening of environmental toxicants: Collision cross sections, structural...

Ion mobility mass spectrometry (IM-MS) is increasingly used in suspect screening of environmental toxicants because it adds an orthogonal gas-phase separation dimension to LC-HRMS workflows. This review evaluates how ion mobility measurements and derived collision cross section (CCS) values support candidate rejection, structural annotation, and fit-for-purpose evidence evaluation for environmental chemicals. The discussion covers drift tube, traveling-wave, trapped ion mobility, and differential mobility approaches; experimentally derived and predicted CCS resources; and applications to PFAS, pesticides, pharmaceuticals, mycotoxins, petroleum contaminants, industrial chemicals, and exposure-related xenobiotics. Three quantitative tables compare CCS resources, application studies, and prediction or complementary annotation tools, with emphasis on compound coverage, tolerances, matrix-dependent ionization and mobility behavior, and evidence criteria. Experimentally derived CCS values can reduce candidate lists, resolve coeluting features, support homologous-series interpretation, and improve transfer of screening evidence across campaigns. Predicted CCS is useful for prioritization but requires class-aware applicability checks, especially for fluorinated, halogenated, surfactant-like, and polymer-associated chemicals that are sparse in training data. CCS is most defensible when reported with ion identity, adduct, drift gas, calibration or derivation method, replicate uncertainty, matrix behavior, and a stated confidence level. IM-MS should therefore be integrated as a supporting evidence layer and not treated as a stand-alone identifier.