title: Difference equation model for isothermal gas chromatography expresses retention behavior of homologues of n-alkanes excluding the influence of holdup time.
abstract: A difference equation (DE) model is developed using the methylene retention increment (Δtz) of n-alkanes to avoid the influence of gas holdup time (tM). The effects of the equation orders (1st-5th) on the accuracy of a curve fitting show that a linear equation (LE) is less satisfactory and it is not necessary to use a complicated cubic or higher order equation. The relationship between the logarithm of Δtz and the carbon number (z) of the n-alkanes under isothermal conditions closely follows the quadratic equation for C3-C30n-alkanes at column temperatures of 24-260 °C. The first and second order forward differences of the expression (Δlog Δtz and Δ2log Δtz, respectively) are linear and constant, respectively, which validates the DE model. This DE model lays a necessary foundation for further developing a retention model to accurately describe the relationship between the adjusted retention time and z of n-alkanes.
authors.affiliation: Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
authors.forename: Liejun
authors.initials: L
authors.lastname: Wu
authors.forename: Yongli
authors.initials: Y
authors.lastname: Chen
authors.forename: Sarah A L
authors.initials: SA
authors.lastname: Caccamise
authors.forename: Qing X
authors.initials: QX
authors.lastname: Li
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D002849:Chromatography, Gas / Q000379:methods*; D008956:Models, Chemical; D015203:Reproducibility of Results; D013816:Thermodynamics
chemical_list: D000473:Alkanes