Chromatography Forum

I am running a prep system for purification of laboratory samples and am having a pressure problem. The system originally developed a high pressure issue and was running at > 2800 psi and hitting the high pressure limit, halting any running method.
I changed the inlet filter having found this to be the cause of the high pressure problem but have since found a low pressure problem, the sytem runs at ~ 450 psi, also (a) retention times for prep runs have become very long as a result of the pressure and (b) the organic pump head was sounding odd on a few strokes so I changed the piston seal. This resolve the noise issue but my pressure has not recovered.
Additionally, I have noticed that the pressure jumps about a bit, e.g. 435 - 478 - 493 - 464 -478 etc

Any ideas what I should do next?

My system uses Gilson 322 pumps, prep conditions are LUNA 10 C18(2) 250 x 21.20 10u and running 80 - 95 % MeCN, aqueous mp is H2O

Check valves.

sorry,
what am I looking for with the check valves? I have already had a look at the check valve for the organic pump and it appears OK to me. I do not routinely use this system and require some more information from you to determine if something is wrong

Kate,

The thing to look for is whether or not the check valves are seating properly. If you have replacements handy, the simplest thing to do is to pop in a new one and see if this helps. Sometimes you can identify the cause of the problem by just looking at the flow out of the check valve if you have a fluid line connected to it. If the flow is pulsating, you have a problem unless you are using a single piston pumped in which case you have to expect some pulsation. There are other possible problems, though. Perhaps the seal wasn't installed properly. Any evidence of leakage?