Chromatography Forum

I'm curious how to best inject methane to measure column flow. I've seen a setup that Restek sells for filling a manual syringe with methane, but on my 5890 I wouldn't trust my injection technique to get a good retention time. Is there a clever way to do this with a autosampler and a vial?

You can trust your injection technique. For setting the flow, you don't care about how well you can reproduce the size of the methane peak, you just care about how fast it comes out. As long as your detector can see the methane peak, that's really all you need.

I'm curious how to best inject methane to measure column flow. I've seen a setup that Restek sells for filling a manual syringe with methane, but on my 5890 I wouldn't trust my injection technique to get a good retention time. Is there a clever way to do this with a autosampler and a vial?

In this case clever = simple. Blow some methane into the vial, put the septum cap on, inject. As long as you see an on-scale peak you can get the dead time.

Peter

Blowing methane in the vial was my original plan, but it's inevitable that oxygen will get in the vial, and I'm trying to not to introduce oxygen into the column. On the other hand, even if you load the syringe with pure methane, it is certain that some large percentage will exchange with air before the injection occurs.

Is oxygen really not that harmful in these amounts? I've heard of simply injecting air to set column flow.

Under reasonable conditions (1ul injection, 10:1 split, 2 ml/min flow) the oxygen concentration in the carrier gas is 10 micromoles/mole and the column is exposed for 2 min (or a higher concentration in the air plug but for the peak width in time). I doubt it would be a problem.

Peter

Hi

Try using a standard disposable cigarette lighter (flint based type) as a supply of your non retained gas without introducing oxygen

The nozzle bore was designed to accept a standard 10uL syringe needle

Regards

Ralph

What a great idea! I will give that a try.