Chromatography Forum

We run a method using a silica column and pH7.2 mobile phase. A certain school of thought suggests that a saturator column retards the errosion of the analytical column packing. Another school of thought suggests that this is a waste of time.
Wisdom please.

JW

Guard columns can work in "sacraficial mode" as long as you remember to replace them before they're gone. They don't eliminate erosion, but they can retard it some (so I am told).

It is not impossible that the solubility of the silica limits your column life, and that this could be fixed by using a saturator column.

On the other hand, the problem of column life could also be due to contamination. In this case, a guard column would serve you best. A guard column actually will have two functions: it will protect the column from dissolution and from contamination. I would go for the guard column approach.

I have tried the saturator ("precolumn") trick a couple of times -- admittedly years ago. It didn't seem to make any difference.

Thanks for the answers.
Has anyone thought of pre-saturating MP w/ fine silica particles during prep? Filtering afterwards of course.
John

Not that I'm aware of. I'd worry about that on the chance that the solubility of the silica might decrease (e.g., due to a temperature change), resulting in precipitation of silica where you don't want it. (Hey, just because I'm paranoid doesn't mean that someone's not out to get me! ).

Don´t you use glass bottles?
(Is this business of protecting main column dissolution with a guard one of the myths of chrom?)

Yes we do use glass bottles. Good point.
Glass is not the same as column silica, however, and doesn't have as much surface area.

You're probably right in that this is a myth. No one has said it has definitely improved the life of their columns.

John

But consider the time the stuff spends in the glass bottle vs the time in the guard. On the chemical difference? Glass is certainly "dirtier", probably dissolves more easily??