repairing Agilent G1379B degasser

[Baffled Chromatographer]

I've been using an Agilent G1379B degasser in my lab for about 1.5 years now. We've begun to see an accumulation of a salty deposit around the vacuum exhaust line on the front of the solvent drip tray. Since we have never used any salts in our mobile phases, I'm pretty sure that this crusty accumulation is coming from the vacuum pump. Furthermore, upon disassembly of the degasser, I found traces of liquid in the vacuum exhaust line. The solid is also tinged with green (copper?). The degasser has not yet generated any error codes.

All of this leads me to believe that I have a small membrane leak, that solvent has been aspirated into the vacuum pump, and then the solvent (with 0.1% formic acid) is carrying away bits of the vacuum pump as it exits thru the waste line.

My questions are:

• 1. Has anyone else encountered this failure mode?
  2. Any suggestions as to how I figure out which of my 2 vacuum chambers has failed?

[HPLCCONSULT]

From your description, I do not think you have a membrane leak or problem. Since vacuum degassers "suck" the vapor above the liquid out of the system some of the very material that makes up the mobile phase vapor is exhausted. Over time this can result in small deposits forming at the outlet. Anything that is exposed to the solvent vapor (pump components and flow path of degasser) can react or deposit outside. Depending on temperature, some of the material will condense in the exhaust lines. Since you are using a mild to strong acid, the acid vapor is also carried out of the system too.

Ask yourself: How old is the system ? Is the device doing its job ? Is the vac pump running too often or at about the same cycle as usual ? Once a leak forms, the pump will need to run for longer times to try and get the pressure down to the relay trip point. BTW: The manual includes some troubleshooting info as well as info on the set points if interested.

Vac degassers do not last forever and we have seen many fail early in life (1st or 2nd year). Early failures can be due to running strong acids/salts or other incompatible materials through them; not flushing them out often; or abnormal failure of the membrane, pump, relay or pressure sensor to name a few. *I would expect one to last five to ten years under normal conditions.

[Baffled Chromatographer]

HPLCCONSULT: Thanks for talking me down. Over the noise of our MS foreline pump, it's difficult to tell the difference between the "high" and "low" vacuum pump settings (this is the "new" one that runs the vacuum pump all the time), but I can hook up a voltmeter to see what's going on with pump and sensor.