title: Constant holdup times in gas chromatography by programming of column temperature and inlet pressure
abstract: The requirements for attaining constant holdup times in capillary gas chromatography (GC), while linearly programming both column temperature and inlet pressure, are illustrated. A scheme, which is based on a series of responses from isothermal and isobaric conditions, is proposed. The responses from two commonly used GC instruments, one with a mass-selective detector operating at near-vacuum pressure and another with a flame-ionization detector at ambient pressure, are analyzed. A significant deviation from Poiseuille flow is noted due to the use of helium as a carrier gas. Nonetheless, the experimental holdup times are approximately constant over a range of temperatures and pressures. Theoretical analysis reveals the spatial and temporal dependence of flow rates inside the column during the programmed runs.
authors.affiliation: Department of Chemistry, California State University, Chico 95929-0210, USA. tnahir@csuchico.edu
authors.initials: TM
authors.lastname: Nahir
authors.initials: KM
authors.lastname: Morales