Chromatography Forum

Hi everyone

We have a persistant problems with our Dionex DX-120 IC system, which is set up for both anions and cations.

When running anions, everything can be fine and then the baseline can suddenly jump up from zero to as high as 400 uS and the sensitivity increase about 10-fold (causing some of the peaks to be beyond the upper limit of detection). The baseline can stay at this level for days or drop down back to zero straight away or even drop below zero.
Sometimes the machine will be fine, the baseline can be at zero for days and then suddenly it will change mid way through a run or between runs with no warning. There does not appear to be any pattern to it.

The problem only seems to happen for anions, not cations which we also run on our machine. We are using an AS14A column with a carbonate eluent.

It is really annoying when it happens!

If anyone has any suggestions what the problem might be I would be very grateful.

Tim

Tim,

The problem you describe sounds like a problem with the detector electronics. The fact that you only see the problem with anions is probably connected to the higher background conductivity associated with the anion application. I have seen cases where a bad bit on one of the detector range chips would cause problems only with some eluent systems while behaving normally with other eluent systems so you are probably seeing something similar. You could probably verify this by temporarily using a different column with a lower background conductivity, although, it would be a lot more efficient to have a service engineer to take a look at the instrument.

Thanks for the reply. We have ordered a new suppressor and we are going to see if this fixes the problem because it was quite old anyway, but I am not confident that it will.
I will see what happens and post a reply.
Cheers.

So did new suppressor work?

Haven't got it yet! Ordering from the USA so might take a while. Will post a reply when we have it.