Difference equation model for isothermal gas chromatography expresses retention behavior of homologues of n-alkanes excluding the influence of holdup time

► The DE model describes the retention behavior by excluding the influences of hold-up time. ► The quadratic equation has a balance of calculation simplicity and result accuracy. ► Retention behaviors of methane and ethane differ from those of C3 or larger n-alkanes. ► The DE model is developed based on the improved accuracy and precision of GC technology.