title: Pressure-assisted capillary electrophoresis electrospray ionization mass spectrometry for analysis of multivalent anions.
abstract: We describe a method, based on pressure-assisted capillary electrophoresis coupled to electrospray ionization mass spectrometry (PACE/ESI-MS), that allows the simultaneous and quantitative analysis of multivalent anions, such as citrate isomers, nucleotides, nicotinamide-adenine dinucleotides, and flavin adenine dinucleotide, and coenzyme A (CoA) compounds. Key to the analysis was using a noncharged polymer, poly(dimethylsiloxane), coated to the inner surface of the capillary to prevent anionic species from adsorbing onto the capillary wall. It was also necessary to drive a constant liquid flow toward the MS by applying air pressure to the inlet capillary during electrophoresis to maintain a conductive liquid junction between the capillary and the electrospray needle. Although theoretical plates were inferior to those obtained by CE/ESI-MS using a cationic polymer-coated capillary, the PACE/ESI-MS method improved reproducibility and sensitivity of these anions. Eighteen anions were separated by PACE and selectively detected by a quadrupole mass spectrometer with a sheath-flow electrospray ionization interface. The relative standard deviations (n = 6) of the method were better than 0.6% for migration times and between 1.4% and 6.2% for peak areas. The detection limits for these species were between 0.4 and 3.7 micromol/L with pressure injection of 50 mbar for 30 s (30 nL), that is, mass detection limits calculated in the range from 12 to 110 fmol at a signal-to-noise ratio of 3. The utility of the method was demonstrated by analysis of citrate isomers, nucleotides, dinucleotides, and CoA compounds extracted from Bacillus subtilis cells.
authors.affiliation: Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0017, Japan. soga@sfc.keio.ac.jp
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Soga
authors.forename: Yuki
authors.initials: Y
authors.lastname: Ueno
authors.forename: Hisako
authors.initials: H
authors.lastname: Naraoka
authors.forename: Keiko
authors.initials: K
authors.lastname: Matsuda
authors.forename: Masaru
authors.initials: M
authors.lastname: Tomita
authors.forename: Takaaki
authors.initials: T
authors.lastname: Nishioka
mesh_terms: D000838:Anions / Q000032:analysis; D001412:Bacillus subtilis / Q000737:chemistry; D002951:Citrates / Q000032:analysis; D003065:Coenzyme A / Q000032:analysis; D019075:Electrophoresis, Capillary / Q000379:methods*; D009711:Nucleotides / Q000032:analysis; D011312:Pressure; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D000838:Anions; D002951:Citrates; D009711:Nucleotides; D003065:Coenzyme A