title: Does electrospray ionization produce gas-phase or liquid-phase structures?
abstract: Electrospray ionization of tyrosine from a 3:1 (v:v) CH3OH/H2O solution is found to afford an M - H ion which is a 70:30 mixture of phenoxide and carboxylate ions. This corresponds to the gas-phase equilibrium composition and not the liquid-phase proportions. In contrast, the carboxylate is produced as the dominant ion (approximately 95%) from anhydrous CH3CN and CH3CN/H2O mixtures. The addition of small amounts of CH3OH to the solvent, however, convert the M - H ion back into the gas-phase isomeric ratio. The isomeric structure therefore depends on the solvent system from which an ion is sprayed.
authors.affiliation: Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Zhixin
authors.initials: Z
authors.lastname: Tian
authors.forename: Steven R
authors.initials: SR
authors.lastname: Kass
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry*; D005740:Gases / Q000737:chemistry; D006860:Hydrogen Bonding; D062385:Hydroxybenzoates / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry; D015394:Molecular Structure; D044367:Phase Transition; D010636:Phenols / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D014443:Tyrosine / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D002264:Carboxylic Acids; D005740:Gases; D062385:Hydroxybenzoates; D010636:Phenols; D014867:Water; D014443:Tyrosine; D000432:Methanol