Changes occurring with the immobile liquid phase in gas-liquid chromatography : II. The effect on retention volumes

Abstract

The immobile liquid phase of a gas chromatographic column may undergo physical and chemical changes during conditioning and use. Chemical changes are those which affect the difference in chemical potential of a solute between the solution in the partitioning liquid and the vapor state. Macroscopic physical changes are those which change the total amount of liquid and/or its distribution on the support. Microscopic physical redistribution of partitioner occurs until the surface free energy of the liquid is minimal and uniform over the entire liquid surface. This latter redistribution is probably complete within a small fraction of the lifetime of the column. The assumption that the packing consists of impermeable solid particles coated with a uniform liquid film leads to the conclusion that a chemical change which affects Δμ° for the methylene groups of a homologous series changes the slope of the semi-logarithmic plot of retention volume vs. the number of carbon atoms in the molecule whereas the intercept is altered by either a change in Δμ° for the functional groups of the molecule or by a change in the effective cross-sectional area of the partitioner. Evidence is given that the change due to the latter can be calculated by finding the average amount of liquid on the column irrespective of its distribution. The effect of retention by more than one kind of immobile phase is discussed.