Proper guard column Inlet Installation (between analytical column and inlet)/Leak check

A ferrule of the proper size and composition is always required on all GC and GCMS column connections. In general, ferrules are one time use items.

The split/splitless inlet with a 0.25mm id column/guard column installed on a GCMS system should use the short, graphite/vespel 5181-3323 ferrules. (5181-3323 | Agilent)  The column should stick out 4-6 mm past the end of the ferrule, although I like a mm or so higher.  A tiny bit higher is definitely better than a tiny bit too low.  The Self-Tightening column nut makes installation easier G3440-81011 (G3440-81011 | Agilent ) .

The Purge Ultimate Union (PUU) connections with a 0.25 mm id column/guard column must use the Flexible Metal Ferrules, either G2855-28501 (G2855-28501 | Agilent )  or G3188-27501 ( G3188-27501 | Agilent) .   If  you tried a graphite or graphite/vespel ferrule on those connections, there is residue in the Purged Ultimate Union that will cause problems. The PUU will need to be cleaned out, for sure.

The MS transferline connection with a 0.25mm id column can be done two ways.  The brass nut shown 05988-20066  (05988-20066 | Agilent)  requires the long, graphite/vespel 5062-3508 ferrules (5062-3508 | Agilent)  .  The Self-Tightening column nut makes installation easier G3440-81013 (G3440-81013 | Agilent ) and requires the short, graphite/vespel 5181-3323 ferrules as shown above for the inlet.

For leak checking, set the inlet to SPLIT mode, Gas Saver OFF, Split flow 20 ml/min, column flow 1.2 ml/min.  On a 6890 the septum purge is fixed at 3 ml/min.  Make sure that your column configuration is correct. It should show two columns. Column 1 from inlet to AUX# (frequently Aux4, but could be others depending on plumbing), and then column 2 from AUX# to MSD.   Set column 1 flow to 1.1 ml/min and column 2 flow to 1.25 ml/min.   It is required that column 2 is 0.1 to 0.3 ml/min HIGHER than column 1.

The maximum column flow into a 5975C GCMS depends on high vacuum pump type.  The max on a diffusion pump system is 2.0 ml/min. The max on a turbo pump system is 4.  Optimum helium column flow into any Agilent GCMS ion source is 0.8 to 1.4 ml/min.  

Hope that helps.

Thank you very much for that again. This was extremely helpful. I ordered, received and installed all the necessary parts. The system is up and running and leak-free for now. :-)

I have one more question:

If I perform an MSD tune, do I need specific GC settings or does that not really matter? I noticed that in case of the leak the N2/O2 values varied depending on that, but if there is no leak I assume that this would not matter.

You want the GC conditions to match what you'll use when running samples.  If you tune it one way and run it a different way, the tune is not as...tuned.

What matters:  Column flow,  QQQ collision cell flows, and Transferline, Source, and Quad temperatures.

Always run the column(s) in Constant Flow mode.  The tuning absolutely changes with column flow changes.

It takes a good hour or so for the system to become stable after temperature changes.

It takes at least 15 to 20 minutes or so for a QQQ to become stable after Collision Cell flow changes.

Never run with a leak of any consequence. If the leak is before the column the oxygen will break the spine of the stationary phase cross-linking and kill the column. If the leak is after the column, the air will interfere with the molecules and then ions of interest and also oxidize the hot metal pieces inside.  A leak reduces the lifetime of the filaments, quad(s), and electron multiplier.

Thank you Paul. Just saw this now. I would not know how to change the collison cell flows. Is that controlled by the voltage in my MS? What is QQQ? Triple Quadrupole?

Sorry! I added QQQ/Triple Quad information on this reply to you. On your 5975 system ignore the note above and use this revised one: 

Thanks for clarifying. 

Thanks for clarifying.