Chromatography Forum

Dear friends...

I bought a GCMS QP2010 Shimadzu about one year ago and the turbomolecular pump works but the higher vacuum is not reached. I read another topic in this forum that presents another friend with the same problem, i tried all the suggestions on that topic but the problems persists. Anyone knows what is the real problem. I have seen others posting on forums the same problem but i haven't see none progress. Anyone knows what is this problem?

Thanks...

What are your column dimensions and flow rate, and what vacuum are you achieving?

2.0e+001 Pa (pressure achieved until shutdown)

1 ml/min to 1.8 ml/min (flow rate that vacuum starts). Mostly 1.8 ml/min

Column dimensions: 30m x 0.25mm x 0.25 um

That looks like a Pirani gauge (low vacuum) reading, not an ion gauge (high vacuum) reading. If the Pirani gauge reading does not go below 2.0e+001 you have a large air leak into the system. If the system is leak free the reading should go down to about 5e+000. The most common places for a large leak are the column interface to the mass spectrometer and the front opening door on the mass spectrometer. Try re-installing the column with a new nut and ferrule, and when you pump down the mass spectrometer I would recommend not tightening the screw on the mass spectrometer door and push the door against the O-ring after the rough pump starts and let the vacuum draw the door against the O-ring evenly. I have seen leaks when the screw is tightened before pumping down and the door is not sealing evenly around the O-ring.