Chromatography Forum

Hello,

I am having trouble with getting the air/water check to pass on GC-MS.

I was able to determine that the issue is coming from the back inlet by plugging the inlet side of the column and also testing out the air and water check readings when connected to the front inlet.

So far I have tried , changing septum, liner, o-ring, gold seal but I am still getting a relatively high N2 reading.

For reference this is what my air and water check looks like:

Water: 3.01%
Nitrogen: 21.06%
Oxygen: 6.39%
Carbon dioxide: 0.29%

The N2 readings usually fluctuates between 12 and 21%.

Any more steps I should take to correct the back inlet? I am using a split/splitless inlet connected to a headspace sampler.

GC:7890B
MS:5977B
HS:7697A

Hello

1. How do you connect HS to inlet? transfer line with needle or permanently attached to inlet weldment?
2. Have you checked split vent line and trap?

Regards

Tomasz Kubowicz

Is the nitrogen as abundant if you increase the split flow?

I had a port that would show a leak at low split flows but go away at high split flows. I think it turned out to be a bad seal at the bottom on the gold seal interface.

GC:7890B
MS:5977B
HS:7697A

If the 7890B uses an EPC similar to those of the 6890... Then the little block that connects the weldment to the EPC may be leaking at one of the o-rings. There are three of them there and if they get stiff and old they can let air into the inlet.

For the 6890N, those o-rings are Agilent PN# 5181-3344.

Are you running a line from the EPC to the headspace and back? Have you tried Canned air? Set the repeat scan to 45-200 and start spraying?

Best regards,