Chromatography Forum

could someone please explain differences between retention gap and guard column?

So far I understand both of them are connected between the injector and the analytical column with same diameter as the as the analytical column but for different purpose..

guard column - to protect analytical column from contamination (e.g. non-volatiles in split injection mode)

retention gap - can act as guard column; does not protect the analytical column like guard columns do but used primarily for focusing the sample components when the sample is injected directly onto the column..

Hi

see

http://www.restek.com/Technical-Resourc ... orial_A008

http://www.restek.com/Technical-Resourc ... orial_A009

Regards

Ralph

Essentially they are the same thing and can serve dual purpose. If injecting with oven temperature below boiling point of solvent you will get a thin layer of solvent condensed on the bare column and it is considered a retention gap, but it will also trap high boiling and non-volatile components before they can reach the analytical column which makes it a guard column. Name mainly depends on the injection technique. You can inject 5ul in splitless into a cold guard column and it becomes a retention gap, instead of needing an on-column injector.

Hello

You can inject 5ul in splitless into a cold guard column and it becomes a retention gap, instead of needing an on-column injector.

If you have thermally unstable analytes COC sometimes is the only option. S/SL inlet will not replace cool on column in all cases.

Regards

Tomasz Kubowicz

It has two purposes, but I think the guarding purpose is more than the gap. But, it fact it's a gap.