title: Ionization of unconjugated, glycine- and taurine-conjugated bile acids by electrospray ionization mass spectrometry.
abstract: We investigated the effect of organic anions as spray liquid additives on the ionization efficiency of unconjugated, glycine-conjugated and taurine-conjugated bile acids under electrospray ionization conditions. Addition of organic acids influenced the ionization efficiency of whole bile acids. Use of a stronger acid reduced the peak intensity of unconjugated and glycine-conjugated bile acids, while the use of TFA, the strongest acid tested, improved the intensity of taurine conjugates. The hydroxyl group at the C-12 alpha position of cholic acid and deoxycholic acid easily underwent intra-molecular hydrogen bonding with the side chain carboxyl group, accelerating the ionization efficiency. This intra-molecular hydrogen bond may also affect the formation of product ions in low energy-CID. The addition of ammonium ions to the spray liquid influenced the ionization of all bile acids, specifically enhancing the ionization efficiency of unconjugated bile acids.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama, Aoba-ku, Sendai 980-8578, Japan.
authors.forename: Nariyasu
authors.initials: N
authors.lastname: Mano
authors.forename: Masaru
authors.initials: M
authors.lastname: Mori
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ando
authors.forename: Takaaki
authors.initials: T
authors.lastname: Goto
authors.forename: Junichi
authors.initials: J
authors.lastname: Goto
mesh_terms: D001647:Bile Acids and Salts / Q000032:analysis*; D005998:Glycine / Q000032:analysis*; D006860:Hydrogen Bonding; D007202:Indicators and Reagents; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D013654:Taurine / Q000032:analysis*
chemical_list: D001647:Bile Acids and Salts; D007202:Indicators and Reagents; D000644:Quaternary Ammonium Compounds; D013654:Taurine; D005998:Glycine