A Mass Spectrometry Method for the Determination of Enantiomeric Excess in Mixtures of d,l-Amino Acids

• Published in: Analytical chemistry (Washington) 2000-09, Vol.72 (18), p.4275-4281
• Main Authors: Grigorean, Gabriela, Ramirez, Javier, Ahn, Seong He, Lebrilla, Carlito B
• Format: Article
• Language: English
• Subjects: Amino acids; Amino Acids - analysis; Aminoacids, peptides. Hormones. Neuropeptides; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Chemistry; Cyclodextrins; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Indicators and Reagents; Mass spectrometry; Organic chemistry; Proteins; Reactivity and mechanisms; Scientific imaging; Spectrometry, Mass, Electrospray Ionization; Stereoisomerism
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac000061f

A mass spectrometry method based on ion/molecule reactions for determining enantiomeric excess in mixtures of amino acids is illustrated. Protonated complexes of amino acids with β-cyclodextrin are produced in the gas phase using electrospray ionization. Under a background pressure of N-propylamine, the amino acid is replaced by the alkylamine. The rates of the guest exchange reaction vary with the chirality of the amino acid. A calibration curve employing varying mixtures of d- and l-amino acids is produced and the fractions of the d isomer in the test mixtures are determined. The quality of the curve is compared to the chiral selectivity of the reaction. In general, the best calibration curves are obtained in systems with the greatest selectivity.