Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
J Chromatogr A. 2012 Oct 19;1260:215-23. doi: 10.1016/j.chroma.2012.07.077. Epub 2012 Aug 1.
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.
采用亚甲基保留增量（Δtz）建立差分方程（DE）模型，以避免气体滞留时间（tM）的影响。该方程阶数（1 阶至 5 阶）对曲线拟合准确性的影响表明，线性方程（LE）不太令人满意，没有必要使用复杂的立方或更高阶方程。在等温条件下，Δtz 的对数与正构烷烃的碳原子数（z）之间的关系密切遵循 24-260°C 柱温下 C3-C30 正构烷烃的二次方程。表达式的一阶和二阶前向差分（分别为Δlog Δtz 和 Δ2log Δtz）分别呈线性和常数，这验证了 DE 模型。该 DE 模型为进一步开发保留模型以准确描述正构烷烃的调整保留时间和 z 之间的关系奠定了必要的基础。
