high pressure errors - help please

[cmcmahan]

We are using an Agilent HPLC Series 1100 with an isocratic pump. We have a high pressure error with mobile phase only (THF). The pressure starts normally but increases in less than a minute. . The source of the high pressure seems to be in the pump area (column has been disconnected). We are using a brand new model Degassex4400 - with no pressure errors indicated.
We have inspected and cleaned the pump, replaced the active inlet valve cartridge, replaced the purge valve and frit, replaced prefilter frit, and replaced the capillary line.
The manual suggests the damper or LPM board. $$$$ ouch.
Any suggestions?
Thank you!

[Kostas Petritis]

Are you sure it is not just backpressure generated from PEEK swelling caused by the THF? Have you had the chance to read the thread at: http://www.sepsci.com/chromforum/viewtopic.php?t=6437

Change the PEEK tubing and try with another solvent. If you do not have any backpressure, then it is just the THF that causes problems and you should not use it with PEEK connections (use stainless steel).

[EnvChemist]

I agree with Kostas,

I just had a problem similar to yours - the pressure ramped to 300 bar in less than 3 minutes. I changed from the sample loop switching the peek finger tight tubings for stainless steel and voila ! Problem solved ...

[cmcmahan]

Thanks to both of you who replied. We had eliminated the PEEK a while back. Turns out the problem was the frit in the purge valve. We had replaced it before the degasser died, so thought it would be fine. When we checked it again it was visibly dirty - I think when the old degasser died it sent material downstream. After the second purge vavle frit we were back up and running.