High Nitrogen Low Water

[JBaltzell]

Hey everyone,

This is my first time asking a question on here, so be kind! I'm brand new to GC-MS, and my training was from a rushed employee in his final two weeks. I wanted someone to either confirm my theory of what's wrong, or give me suggestions about what else could be wrong.

I have been running samples perfectly fine with no issues, but I just trimmed my column and ran an auto tune. The tune showed the following numbers:

H2O: 2.74%
N2: 11.27%
O2: 3.13%
CO2: 1.12%
N2/H2O: 410.89%

I assumed it must be some kind of leak, because I just refitted the column into the inlet. I just found it strange that my water and other values are so low, and the nitrogen is so high. I do feel as though I may have over tightened the inlet, so I was going to try that. Also, I haven't switched out my gas tank, and it was perfect numbers across the board on my last run. Any advice is appreciated!

Josh

[MichaelVW]

Yeah, when I have a bit of a leak I see similar numbers. Oxygen is roughly 1/4th to 1/5th of Nitrogen, just like in the atmosphere. So you're probably right that you need to redo the inlet. You could stab the inlet end of the column into an injection port septum to block it off and see if your N2 drops after a while, or just fix it.

Keep in mind that once you fix the leak, nitrogen will drop pretty quickly but it might take water a little while. Though I don't think 2% water is too bad so it might not move much. Each of my instruments is a little different so it's good to know what to expect from each when you have a good vacuum.

[JBaltzell]

That did it! Thank you so much. I just ran an auto tune and got my usual numbers. Thanks again!