Gas-Phase Chiral Separations by Ion Mobility Spectrometry

This article introduces the concept of chiral ion mobility spectrometry (CIMS) and presents examples demonstrating the gas-phase separation of enantiomers of a wide range of racemates including pharmaceuticals, amino acids, and carbohydrates. CIMS is similar to traditional ion mobility spectrometry, where gas-phase ions, when subjected to a potential gradient, are separated at atmospheric pressure due to differences in their shapes and sizes. In addition to size and shape, CIMS separates ions based on their stereospecific interaction with a chiral gas. In order to achieve chiral discrimination by CIMS, an asymmetric environment was provided by doping the drift gas with a volatile chiral reagent. In this study (S)-(+)-2-butanol was used as a chiral modifier to demonstrate enantiomeric separations of atenolol, serine, methionine, threonine, methyl alpha-glucopyranoside, glucose, penicillamine, valinol, phenylalanine, and tryptophan from their respective racemic mixtures.