By Anonymous on Wednesday, May 12, 2004 - 01:37 pm:
Hi
I've been using an Agilent 1100 HPLC system for the past year. Performance was great until three months ago, when the following problems started to occur:
- the solvent comes out of the degasser full of air bubbles during purging. this stops after a while, but when I conduct the analysis the pressure is too low, compared to what was before, under the same conditions. subsequently, retention times have changed dramatically and are not stable anymore. my solvent system is a mixture of water/ethanol/acetic acid.
I tried to perform the same analysis using a different instrument. After a few very successful runs, similar problems started to arise. I filter my solvents, then degas them in a ultrasound bath. Other people use the same solvents and the same instrument without any such phenomena, even though they don't degas, only filter.
the weird thing is that the solvents enter the online degasser seemingly bubble-free and exit the degasser full of bubbles. i've tried to remove all bubbles from the system with isopropanol, without success. I repeat, this only happens to one person in the lab: me :-(
i've changed the purge valve, the seals and the frits, again to no success.
does anyone have any ideas why this could be?
Maria
By Anonymous on Wednesday, May 12, 2004 - 01:51 pm:
You may have gas in the degasser lines, and might be purging faster than the degasser can pull out all the gases. Turn off pump, wait a few hours. Turn on pump at 5 ml/min with each channel 25%, you should be getting gas-free solvents.
By Anonymous on Wednesday, May 12, 2004 - 01:53 pm:
You may have gas in the degasser lines, and might be purging faster than the degasser can pull out all the gases. Turn off pump, wait a few hours. Turn on pump at 5 ml/min with each channel 25%, you should be getting gas-free solvents.
By HW Mueller on Thursday, May 13, 2004 - 11:59 pm:
Maybe at some times you created leaking connections. These may draw in air (Venturi) instead of loosing liquid.
By bill lyons on Friday, May 14, 2004 - 07:44 pm:
Maria,is indicator light on front of the degasser
glowing red? Can you hear the little vacuum pump come on? The unit most likely needs repair.
A sticking solenoid valve in the degasser can be very frustrating.One moment you have vacuum... next you don`t.