Hello,

I am a little confused about the pre-column and guard column. Could anyone give me a detail explanation of their difference and their application.

Thanks in advance!

A pre-column comes before the injector, and it is packed with silica to saturate an alkaline mobile phase, so it won't attack a silica-based analytical column. If your mobile phase is properly filtered, you shouldn't ever need to replace the pre-column (until a significant portion has dissolved away).

A guard column comes after the injector, and it is packed with the same packing used for the analytical column, so anything that would gum up the frits or packing is caught on the guard column first. When the required pump pressure starts to rise or when the peaks for standards are noticably broader than for runs made when the analytical column was new, replacing the guard column hopefully will restore the performance of the system.

Hello,
I don't wonder about the confusion. Many terms are used, and sometimes the meaning is different. And than we also have different understanding in different languages.
In Germany we often use this deffinition:
A column before the injector is called "Saettigungssaeule"(Saturator column)
A column after the injector, befor the analytical column, is called "Vorsaeule"(Pre-column) or "Schutzsaeule"(Guard column)!
And you should always protect your analytical column by a short column, no matter how you name it! Gerhard

I not so sure about the general utility of either.

In our pharmaceutical lab we usually filter any samples that may contain particulate or use a precolumn filter. I have seen little reason to use a guard column.

For reverse phase columns we rinse the buffers from our column and remove strongly retained impurities with 100% ACN with an automated shutdown procedure after every run. We store the columns in 100% ACN. Our columns generally last many thousands of injection without a guard column.

As for a saturator column, I think it is better to use a modern base stable column. If your current system doesn't have a saturator column and you install one it will increase your system dwell volume and could affect resolution for gradient methods.

Your particular sample may require the use of a guard column or a specific method may benifit from a saturator column, but we run hundreds of thousands of samples a year without either.