{"doi":"10.1021/jasms.5c00099","title":"Mass Spectral Analysis of Sterols and Other Steroids in Different Ionization Modes: Sensitivity and Oxidation Artifacts","abstract":"High Resolution Image Download MS PowerPoint Slide In the course of synthetic work and mass spectrometry (MS) with hydroxy steroids, we observed not only the loss of H 2 O but prominent 2 and 4 amu losses using atmospheric pressure chemical ionization (APCI), leading to confusion of the structural assignments. This loss of 2 amu, which we attributed mainly to oxidation of hydroxyls, varied among 44 steroids and sterols analyzed; 36 showed losses of 2 n amu in APCI MS analysis (17/22 Δ 5 steroids, 17/19 Δ 4 steroids, and 2/3 estrogens). With the Δ 5 steroids and sterols, the precursor MH + was either observed as a minor ion or (more frequently) not detected at all, constituting the base peak in 7/22 cases. With heated electrospray ionization (HESI) MS, 2 n amu losses were detected (generally weakly) in 9/44 cases but constituted the base peak in 3/9. In general, the sensitivity (base peak intensity) of steroids correlated with conjugation of the of the steroid frame. Δ 4 steroids generally performed best on HESI + (up to a maximum factor of 8-fold), while Δ 5 steroids and sterols performed better on APCI + (up to >137-fold), except for two trihydroxypregnanes. Estrogens did not show a clear trend. Sensitivity generally increased with the use of NH 4 F as a mobile phase additive in ESI + (up to a maximum of 7-fold). We conclude that the prominence of 2 n amu losses is variable among steroids and sterols but is more commonly an artifact of APCI MS. These m / z losses can constitute dominant ions that impede detection of the precursor MH + and complicate structural assignments.","journal":"Journal of the American Society for Mass Spectrometry","year":2025,"id":526101,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":3,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9562,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2025-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":263589,"name":"F. Peter Guengerich","orcid":"0000-0002-7458-3048","position":1,"is_corresponding":false},{"id":377094,"name":"Kevin D. McCarty","orcid":"0000-0003-0027-9120","position":0,"is_corresponding":true}],"reference_count":45,"raw_metadata":null,"created_at":"2026-07-19T02:50:25.860105Z","pmid":"40574312","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}