Chromatography Forum

Funding is super tight right now, and we have a handful of C18 guard columns already in the lab. Will I be able to use them on a C8 column? The separation could easily be done on a C18 column, however, a C8 was ordered by mistake and then put into use by before the error was realized. Adding insult to injury it's 1.8um packed

That depends on the relative sizes of the column and guard, on the complexity of the sample, and on the robustness of the separation.

If the bed volume of the guard is small compared to that of the column, then you are only making a small change to the chemistry; if there are not too many closely spaced peaks, and if the separartion is robust with respect to C8 vs C18, then you should be OK. My guess is that you probably won't have any problem.

Do try it, and please report back! I'd be slightly worried that you're putting a more retentive material on the top of your column, so particularly with a gradient method, isn't there a danger of considerably delayed peaks? I'd love to know, because this is the sort of thing that's bound to happen in my lab sooner or later, and I'd like to know the symptoms so I'll spot it when it does.

Wouldn't a more retentive guard column help prolong the analytical column by retaining even more crud? I wouldn't think it was an issue, although the 1.8um column might be!!

Wouldn't a more retentive guard column help prolong the analytical column by retaining even more crud?

If the crud will pass through the analytical column, then there is no point to retaining it on the guard -- better to just let it wash through. The idea is to catch stuff that would be irreversibly retained by the analytical column.

So what was the outcome? Did it work OK? Did you see any differences?