Ionization of unconjugated, glycine- and taurine-conjugated bile acids by electrospray ionization mass spectrometry.
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.
Mano
Nariyasu
N
Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama, Aoba-ku, Sendai 980-8578, Japan.
Mori
Masaru
M
Ando
Masayuki
M
Goto
Takaaki
T
Goto
Junichi
J
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*
D001647:Bile Acids and Salts; D007202:Indicators and Reagents; D000644:Quaternary Ammonium Compounds; D013654:Taurine; D005998:Glycine