title: Factors influencing the electrospray intrasource separation and selective ionization of glycerophospholipids.
abstract: The external electric field induces a separation of cations from negative electrolyte ions in the infusate while differential ionization of molecular species that possess differential electrical propensities can be induced in either the positive- or negative-ion mode during the electrospray ionization process. These physical and electrical processes that occur in the electrospray ion source have been used to selectively ionize lipid classes possessing different electrical propensities that are now known as "intrasource separation and selective ionization". However, the chemical principles underlying charge-dependent alterations in ionization efficiencies responsible for the selective ionization of lipid classes are not known with certainty. Herein, we examined the multiple factors that contribute to intrasource separation and selective ionization of lipid classes under optimal instrumental conditions. We demonstrated that many different lipid classes could be selectively ionized in the ion source and that intrasource resolution of distinct molecular constituents was independent of lipid concentration, flow rate, and residual ions under most experimental conditions. Moreover, the presence of alkaline conditions facilitates the selective ionization of many lipid classes through a mechanism independent of the design of the ESI ion source. Collectively, this study provides an empirical foundation for understanding the chemical mechanisms underlying intrasource separation and selective ionization of lipid classes that can potentially be used for global analysis of cellular lipidomes without the need for chromatographic separation.
authors.affiliation: Division of Bioorganic Chemistry and Molecular Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA. xianlin@wustl.edu
authors.forename: Xianlin
authors.initials: X
authors.lastname: Han
authors.forename: Kui
authors.initials: K
authors.lastname: Yang
authors.forename: Jingyue
authors.initials: J
authors.lastname: Yang
authors.forename: Kora N
authors.initials: KN
authors.lastname: Fikes
authors.forename: Hua
authors.initials: H
authors.lastname: Cheng
authors.forename: Richard W
authors.initials: RW
authors.lastname: Gross
mesh_terms: D000465:Algorithms; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D045424:Complex Mixtures / Q000032:analysis; D020404:Glycerophospholipids / Q000737:chemistry* / Q000302:isolation & purification; D007262:Infusions, Intravenous; D010743:Phospholipids / Q000737:chemistry / Q000302:isolation & purification; D012996:Solutions; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D045424:Complex Mixtures; D020404:Glycerophospholipids; D010743:Phospholipids; D012996:Solutions