Chiral Carbohydrate Adducts are Effective for Enantiomeric Ion Mobility Separations

Abstract

Enantiomers play important roles in biology and the pharmaceutical industry but remain notoriously difficult to separate and characterize. Gold-standard chromatography and nuclear magnetic resonance-based methods are slow, laborious, and expensive, motivating the development of rapid methodologies for enantiomer characterization. While ion mobility spectrometry-mass spectrometry (IMS-MS) has emerged as a rapid technique for chiral analysis, current approaches often rely on derivatization, complicated chiral complexes, or large host molecules that can produce complex spectra. Herein, we investigate small carbohydrates as chiral adducts for the ion mobility separation of amino acid and drug enantiomers. Six commercially available nonreducing or reduced carbohydrates were evaluated as chiral adduct molecules using cyclic IMS-MS. All carbohydrate adducts readily formed simple 1:1 complexes in the MS dimension that produced two discrete IMS peaks for each enantiomeric pair and remained sufficiently stable for extended path length separations. The carbohydrate panel enabled chiral separation of all 15 amino acid and drug enantiomer pairs at pathlengths as low as 1 m. Relative arrival time measurements further enabled unbiased comparison of separation performance across analyte-adduct pairs. The developed carbohydrate-based method was used to quantify enantiomeric excess down to a 99:1 molar ratio with estimated limits of detection down to 5 nM. These results demonstrate that small carbohydrates are effective chiral adducts for IMS-MS-based enantiomer separations and that simple analyte-adduct complexes can provide rapid and broadly applicable enantiomer differentiation without derivatization or the use of multimolecule complexes.