title: Column temperature programming in enantioseparation of dihydropyrimidinone compounds using derivatized cellulose and amylose chiral stationary phases.
abstract: We report the application of column temperature programs as a tool to examine unusual temperature-induced behaviors of polysaccharide chiral stationary phases (CSPs). Using dihydropyrimidinone (DHP) compounds as probes we observed the heating (10-50 degrees C) and cooling (50-10 degrees C) van't Hoff plots of retention factors and/or selectivities of DHP compounds were not superimposable on AD, IA, and AS-H columns solvated with ethanol (EtOH)/n-hexane (n-Hex) mobile phases. The plots were not superimposable on AD, IB, and AS-H columns solvated with 2-propanol (2-PrOH)/n-Hex mobile phases. The thermally induced path-dependant behaviors were caused by slow equilibration as evidenced by the disappearance of the hysteresis in the second heating to cooling cycle and in a cooling to heating cycle. From the step-temperature program (10-50-10 degrees C), only EtOH solvated AD and AS-H phases showed the change of retention factors and/or selectivities with time while only 2-PrOH solvated AS-H phase showed similar behaviors.
authors.affiliation: Analytical Chemistry, Amgen Inc., Thousand Oaks, CA, USA. fwang@amgen.com
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.forename: David
authors.initials: D
authors.lastname: Yeung
authors.forename: Jun
authors.initials: J
authors.lastname: Han
authors.forename: David
authors.initials: D
authors.lastname: Semin
authors.forename: James S
authors.initials: JS
authors.lastname: McElvain
authors.forename: Janet
authors.initials: J
authors.lastname: Cheetham