Kinetic plots for gas chromatography: Theory and experimental verification

• Analytical expressions for the kinetic plot method for thin-film GC are derived.
• An analytical solution for kinetic performance limit (KPL) of GC is derived.
• The difference between kinetic plots at maximal versus optimal Δp is demonstrated.
• Experimental confirmation of the expressions was obtained on coupled columns.

Mathematical kinetic plot expressions have been established for the correct extrapolation of the kinetic performance measured in a thin-film capillary GC column with fixed length into the performance that can be expected in a longer column used at the same outlet velocity but at either the maximal inlet pressure or at the optimal inlet pressure, i.e., the one leading to an operation at the kinetic performance limit of the given capillary size. To determine this optimal pressure, analytical solutions have been established for the three roots of the corresponding cubic equation. Experimental confirmation of the kinetic plot extrapolations in GC has been obtained measuring the efficiency of a simple test mixture on 30, 60, 90 and 120 m long (coupled) columns.