Determination of enantiomeric composition by negative-ion electrospray ionization-mass spectrometry using deprotonated N-(3,5-dinitrobenzoyl)amino acids as chiral selectors

The ability to use mixtures of deprotonated N-(3,5-dinitrobenzoyl)amino acids as chiral selectors for the determination of enantiomeric composition by electrospray ionization-mass spectrometry is demonstrated. For each experiment, two N-(3,5-dinitrobenzoyl)amino acids were chosen such that each would have opposite selectivity for the enantiomers of the analyte. Electrospray ionization-mass spectrometry, monitored in the negative ion mode, of solutions containing the two N-(3,5-dinitrobenzoyl)amino acids, sodium hydroxide, and the analyte, in a one-to-one mixture of methanol and water, afford peaks in the mass spectrum that correspond to the deprotonated 1:1 analyte-selector complexes. The ratio of the intensities of the complexes in the mass spectrum can be related to the enantiomeric composition of the analyte. Additionally, the sense and extent of chiral recognition is consistent with chromatographic observations, using chiral stationary phases derived from N-(3,5-dinitrobenzoyl)amino acids. Each analysis of enantiomeric composition requires less than 10 s to complete, indicating that this method has great potential for the development of fast-/high-throughput chiral analyses.