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

PABLO J. LEBED, SONIA KEUNCHKARIAN, JAIVER OSORIO GRISALES, CECILIA B. CASTELLS

JOURNAL OF CHROMATOGRAPHY - A

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013

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 usingcapillary  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  enantiomer-chiral  selector  association  constants  were  then  calculatedfrom  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.