Chromatography Forum

Hi all,

I'm not very experimented with HPLC's and I have an issue with my Waters 2596 HPLC. The pressure is dropping every time I hear the pump and it comes back to normal right after.

Ex: Constant pressure of 2000psi, drop to 1600 right after the pump noise and comes back to 2000psi one second later.

I changed the frit, (I'm running 10%MeOH in MQH2O), It is not caused by air, I purge everything and the degasser is on. In other words, the problem is from the pump. I changed the seals and the plunger, still the same problem.

What else should I check? Does any of you had this problem before?

Thanks

It is probably a check valve issue.

The check valve were changed..

I just ran the outlet part of the inline filter after pump2 to another HPLC, same model/year and the problem still occur, proving that it is caused by the pumps themself.

I just tried using a different line + degass and it doesn't change anything.

I'm out of idea

Any other input ?

HI,
We had the same problem last week. Everyone told us the same thing that it had to be the check valves. For us the problem was not the check valves but dirty plungers, I think. After we took apart the pump head assembly to replace the seal face washers, we noticed some dried white powder on the plungers. I believe it is from switching from a buffered mobile phase to a non aqueous reverse phase without running enough water threw first. After cleaning the plungers and putting everything back together the delta pressure is well within acceptable ranges

good luck

My suggestions are:
1) Replace check-valves ones more
2) Disconnect the inlet-filters from the solvent bottles
3) Connect a bottle of degassed solvent (e.g. ultrasonic bath) directly to the pump, without using GPV (Gradient Proportian Valve, where the Channels A-D go together) or degasser. Maybe the GPV is defect, I have observed this once with a Waters 2795.

I will do all that tomorrow and keep you update

Thanks again for your time!

try to Apply PM KITS .. at least for pump and your problem will gone away,
note : to insure from GPV performance, one of methods are gpv test at waters Qualification protocol.

I will do all that tomorrow and keep you update

Thanks again for your time!

Are there any news to your topic?

Unfortunatly, many posters forget to publish the solution for the problem here.

Regards
Klaus

Unfortunatly, many posters forget to publish the solution for the problem here.

/sign

I haven't had the time to do anything yet, but I will give you an update no matter the upcome, don't worry !

just a 4-5 months FYI follow-up

We notice a leak from the mobile phase to the seal wash. Even after doing PM three times, the problem was persistant. After doing a lot of troubleshooting by swaping parts from a good one (same model), we found the problem. We need to change the head unit assembly, looks like the problem is a micro-scratch next to a seal.

Thanks! It's always nice to find a "happy ending"!