Here's why:

* Non-polar stationary phase: Non-polar GC columns have a stationary phase that is non-polar, like a silicone oil. This means it interacts more strongly with non-polar analytes.

* Boiling point: Compounds with lower boiling points are more volatile and have weaker intermolecular forces. This means they spend less time interacting with the stationary phase and move through the column faster.

* Intermolecular forces: Weaker intermolecular forces, such as London dispersion forces, are weaker than stronger forces like hydrogen bonding or dipole-dipole interactions. Compounds with weaker intermolecular forces will be less attracted to the stationary phase and elute earlier.

Therefore, in a non-polar GC column, the order of elution is generally:

1. Highly volatile, non-polar compounds: These have the lowest boiling points and weakest intermolecular forces.

2. Less volatile, non-polar compounds: These have higher boiling points and stronger intermolecular forces.

3. Polar compounds: These have the strongest interactions with the non-polar stationary phase and elute last.

Examples:

* Hexane will elute before octane in a non-polar column because it has a lower boiling point.

* Benzene will elute before ethanol because it is non-polar and ethanol is polar.

Remember that the exact order of elution can be influenced by factors like the specific stationary phase, column temperature, and carrier gas flow rate.