[ccp4bb] air bubbles in the Bio-Rad Duoflow system

[Ailong Ke]

Hello All,

I own a Bio-Rad Duoflow system for almost a year. The machine lived 
up to some of the recommendations I saw on this board. However, there 
is this annoying problem with air bubbles entering columns and I 
cannot figure out the source. The system would be free of any air 
bubbles in the beginning, and performs fine when water is loaded 
using needle/syringe into the 5ml superloop and then injected into 
the column. When protein samples are injected the same way, a lot of 
air bubbles would appear and get trapped inside the ion exchange 
column, leaving yellowish marks on the Uno columns and eventually 
reducing their performance. I've been a FLC/AKTA user for about ten 
years and have never seen such problems. I doubt it is due to a 
faulty injection valve because we recently had it replaced for other 
reasons. We did move a backpressure generator (a little black piece) 
from post-column position to before-column, otherwise we cannot run 
sizing columns in a reasonable flow rate.

I'd like to hear if you have similar experiences and how you fixed 
the problem. Thanks a lot!

Ailong

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