Determination and evaluation of gas holdup time with the quadratic equation model and comparison with nonlinear models for isothermal gas chromatography

摘要

Gas holdup time (t_M) is a basic parameter in isothermal gas chromatography (GC). Determination and evaluation of t_M and retention behaviors of n-alkanes under isothermal GC conditions have been extensively studied since the 1950s, but still remains unresolved. The difference equation (DE) model [J. Chromatogr. A 1260: 215-223] reveals retention behaviors of n-alkanes excluding t_M, while the quadratic equation (QE) model [J. Chromatogr. A 1260: 224-231] including t_M is suitable for applications. In the present study, t_M values were calculated with the QE model, which is referred to as t_(MT), evaluated and compared with other three typical nonlinear models. The QE model gives an accurate estimation of t_M in isothermal GC. The t_(MT) values are highly accurate, stable, and easy to calculate and use. There is only one t_(MT) value at each GC condition. The proper classification of t_M values can clarify their disagreement and facilitate GC retention data standardization for which t_(MT) values are promising reference t_M values.