Measurements of association constants between enantiomers and chiral selectors by capillary gas chromatography. Theoretical and practical consideration

LEBED, P. J.; KEUNCHKARIAN, S.; OSORIO GRISALES, J.; CASTELLS, C. B.

JOURNAL OF CHROMATOGRAPHY - A

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2014 vol. 1324 p. 198 - 206

0021-9673

The association constants of several volatile enantiomers with octakis(3-O-butanoyl-2,6-di-O-pentyl)-γ-cyclodextrin at temperatures between 50 and 100 °C were measured by gas-liquid chromatography using capillary columns coated with different amounts of chiral selector dissolved in polysiloxane OV-1701 and prepared with a precisely determined phase ratio. Simple expressions were deduced to estimate the apparent distribution constants from accurate hold-up and retention times along with that known phase ratio at each temperature. The absolute enantiomer-chiral selector association constants were then calculated from the linear regression of the apparent constants as a function of the chiral selector concentration. One aim of this study consisted in discussing all the experimental uncertainties inherent in the determination of enantiomer/selector association constants with chiral analytes, and how these fundamental measurements can be performed precisely without resorting to the use of reference solutes.