Chiral Separations Using IMS

A special case of the dependence of IMS separations on the media is chiral analysis. The paramount role of chirality in biology, medicine, and pharmacy has turned chiral 

Tme enantiomers have identical transport and other physical properties and are not separable by physical means including IMS using nonchiral or racemic media. However, enantiomeric ions should have unequal interaction potentials with chiral molecules and thus different mobihties in chiral buffers. That is analogous to a different strength of adsorption of enantiomers in solution on chiral solids or micelles that allow chiral chromatography. A molecule needs some minimum size to possess 

FIGURE 1.17 Extensive coalescence of gas molecules on ions in IMS under certain conditions is demonstrated by the mass spectrum of species produced by passing C04 through moist CO2 at E = 760 Torr and room T. The masses (Da) are given for each peak. The major sequence of nonshaded peaks is for C04 (C02) , shaded features are for C04 H20 (C02) . (From Ellis, H.W., Pai, R.Y., Gatland, I.R., McDaniel, E.W., Wemlund, R.F., Cohen, M.J., J. Chem. Phys., 64, 3935, 1976.) 

The mobilities of two ions with different propensity for gas adsorption depend on the temperature unequally, making their relative mobility a function of T over the relevant range. Hence, besides a universal effect on / , changing the gas temperature may affect the resolution of individual features in conventional IMS and even invert the order of separation. For example, the butanone dimer and 4-heptanone ions have opposite separation orders in N2 at 18 and 80 

The gas pressure is absent from Equation 1.23 and normally does not affect the 

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