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- Posts: 1
- Joined: Fri Nov 01, 2019 12:50 am
With the quaternary pump on (1 mL/min) I can switch between mainpass and bypass just fine, with just a small pressure drop (15 bar with C18 column attached) when going from bypass to mainpass which recovers within about 10 secs. However, sporadically this pressure drop increases to >50 bar during injections (immediately after switch from bypass back to mainpass) which recovers within about 30 secs, with concomitant loss of sample peak size. I can't see any sign of leaks, and pressure test (in bypass) is fine.
Things I've tried:
1) Removing 900uL seat extension (the pressure drop coincided with dripping out of the waste port throughout the injection cycle)
2) Replacing rotor seal and stator face, and replaced analytical head (with a used one)
Everything was back to normal for a few days, but it's happening again (even without the seat extension) with increasing frequency. There must be a leak somewhere (the waste port is fine and only drips as analytical head positions itself to aspirate), but no signs of a leak at the 6-port valve or the analytical head.
Any suggestions appreciated.