<p><a>Racemic mixtures of twelve common </a>a-amino acids and
three chiral drugs were tested for the separation of their enantiomers by ion
mobility spectrometry (IMS)-quadrupole mass spectrometry (MS). Separations were
tested by introducing chiral selectors in the mobility spectrometer buffer gas.
(R)-α-(trifluoromethyl) benzyl alcohol, (R)-tetrahydrofuran-2-carbonitrile,
(L)-ethyl lactate, methyl (S)-2-chloropropionate, and the R and S enantiomers
of 2-butanol and 1-phenyl ethanol were evaluated as chiral selectors. Experimental
conditions were varied during the tests including buffer gas temperature,
concentration, and type of chiral selectors, analyte concentration,
electrospray voltage, electrospray (ESI) solvent pH, and buffer gas flow. The individual
enantiomers yielded different drift times for periods of up to 8 hours in a few
experiments; such drift times were sufficiently different (~ 0.3 ms) to
partially resolve the enantiomers in racemic mixtures, but these mixtures
always yielded a single mobility peak at the experimental conditions tested
with a drift time similar to that of one of the enantiomers. Energy
calculations of the chiral selector –ion interactions showed that these
separations are unlikely using 2-butanol as chiral selector but they might be feasible
depending on the nature of chiral selectors and the type of enantiomers.</p>
On the Separation of Enantiomers by Drift Tube Ion Mobility Spectrometry
