Chromatography Forum

Hi everyone

Is there any guideline/protocol of how often the main column and the guard column should be changed? I am using them for three years and I've been noticing the reduction of retention time.

I don't know if the column can be washed and/or if there is a procedure to do so.

Our main column is Dionex IonPac AS18 (4*250mm) with a P/N of 060549 (Installed Sep 2021)
Our guard column is Dionex IonPac AG18 (4*50mm) with a P/N of 060551 (Installed Sep 2021)

Thanks

They recommend changing the guard column frequently to help preserve the more expensive main column but I have never found that to work. I get about a year out of my As-18s before resolution becomes too poor to give accurate results. If you don't care about sulfate the column can last years I suppose. The problem is that as the column ages bromide and sulfate coelute. We rarely see Bromide in water but you cannot just assume it isn't there when analyzing for sulfate. I actually had a guy from Theromofisher tell me I could ignore the possibility because Br was not seen in water. But you can see it in coastal waters because ocean water has it. There are also bromide discharged from coal power plants and mines. I saw a sample with about 10 mg/L bromide once and it was not near coal or the ocean.

Turning down the EG works to separate bromide-sulfate as the column ages but eventually sulfate and nitrate will be too close when it is lowered. There was an idiot in my lab who would turn the EG up to 27-30 mM to better separate the Bromide sulfate and Nitrate because she chose to ignore the resulting carbonate coelution with Nitrite.

Hi,
Maybe this protocol may help you Protocol of Immobilized Metal Affinity Chromatography