title: Measurements of association constants between enantiomers and chiral selectors by capillary gas chromatography. Theoretical and practical considerations.
abstract: 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 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.
authors.affiliation: Laboratorio de Investigación y Desarrollo de Métodos Analíticos (LIDMA), División Química Analítica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 y 115 (1900) La Plata, Argentina.
authors.forename: Pablo J
authors.initials: PJ
authors.lastname: Lebed
authors.affiliation: Laboratorio de Investigación y Desarrollo de Métodos Analíticos (LIDMA), División Química Analítica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 y 115 (1900) La Plata, Argentina.
authors.forename: Sonia
authors.initials: S
authors.lastname: Keunchkarian
authors.affiliation: Laboratorio de Investigación y Desarrollo de Métodos Analíticos (LIDMA), División Química Analítica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 y 115 (1900) La Plata, Argentina.
authors.forename: Jaiver
authors.initials: J
authors.lastname: Osorio Grisales
authors.affiliation: Laboratorio de Investigación y Desarrollo de Métodos Analíticos (LIDMA), División Química Analítica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 y 115 (1900) La Plata, Argentina. Electronic address: castells@isis.unlp.edu.ar.
authors.forename: Cecilia B
authors.initials: CB
authors.lastname: Castells
mesh_terms: D002849:Chromatography, Gas / Q000295:instrumentation / Q000379:methods*; D013237:Stereoisomerism; D013696:Temperature; D013816:Thermodynamics; D047408:gamma-Cyclodextrins / Q000737:chemistry
chemical_list: D047408:gamma-Cyclodextrins; C023792:gamma-cyclodextrin
keywords: Association constants; Capillary columns; Chiral gas–liquid chromatography; Octakis(3-O-butanoyl-2,6-di-O-pentyl)-γ-cyclodextrin