4.2.1 Basic Chromatography Theory

A GC separation, like extraction, involves a partitioning of solutes between phases. In the case of GC, one phase in stationary and the other is mobile. The more a solute is partitioned in the mobile phase, the more it moves; in other words, the partitioning between the stationary and mobile phases affects the time required for a solute to travel through the instrument.

• A solute that interacts very little with the stationary phase (via van der Waals forces such as dispersion, dipole-dipole interactions, etc.) moves relatively quickly through the column. Such a solute is not retained by the stationary phase material.
• A solute with strong interactions with the stationary phase is retained by that phase; such a solute will take longer to travel through the column.

This is essentially the same for all types of chromatography (thin layer, paper, liquid-liquid, etc). Gas chromatography is more precisely described as gas-liquid chromatography.