Publication Details (including relevant citation information):
Anal. Chem. 82: 9967-9976
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.
Address (URL): http://pubs.acs.org/doi/abs/10.1021/ac1019039