title: Simultaneous analysis of amino acids and carboxylic acids by capillary electrophoresis-mass spectrometry using an acidic electrolyte and uncoated fused-silica capillary.
abstract: A simple, low-cost capillary electrophoresis-mass spectrometry (CE-MS) method is demonstrated for the simultaneous analysis of amino acids and small carboxylic acids (glycerate, lactate, fumarate, succinate, malate, tartrate, citrate, iso-citrate, cis-aconitate, and shikimate). All CE-MS experiments were performed using a single uncoated fused-silica capillary and with a single separation electrolyte, formic acid. For CE polarity, the CE inlet was set as the anode, and the MS side was set as the cathode. By using high-speed sheath gas flow, the apparent mobilities of all compounds were sped up; thus, the migration times of the carboxylic acids were reduced. In positive ion mode ESI-MS detection, small carboxylic acids were detected faintly as m/z = [M + 18](+) or [M + 23](+), after protonated molecule detection (m/z = [M + 1](+)) of the amino acids. In negative ion mode, all of these small carboxylic acids were detected clearly as deprotonated molecules (m/z = [M - 1](-)), after detection of the amino acids. By changing the polarity of the MS during CE separation, both amino acids and small carboxylic acids were detectable in a single electrophoresis analysis run. With this method, the diurnal metabolic changes of pineapple leaves were observed as reflecting Crassulacean acid metabolism.
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Wakayama
authors.forename: Naohiro
authors.initials: N
authors.lastname: Aoki
authors.forename: Haruto
authors.initials: H
authors.lastname: Sasaki
authors.forename: Ryu
authors.initials: R
authors.lastname: Ohsugi
mesh_terms: D000596:Amino Acids / Q000032:analysis*; D002264:Carboxylic Acids / Q000032:analysis*; D004573:Electrolytes; D019075:Electrophoresis, Capillary / Q000295:instrumentation / Q000379:methods*; D004867:Equipment Design; D013058:Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D012822:Silicon Dioxide
chemical_list: D000596:Amino Acids; D002264:Carboxylic Acids; D004573:Electrolytes; D012822:Silicon Dioxide