Headspace liners

[pstaunton]

Just a question about the best I.d liner to use with headspace.

I assume since the sample is already a vapour when it enters the liner that back flash should not be a problem. Is this correct?

Is there any drawbacks from using narrow 2mm I.d liners.

[Peter Apps]

If all the gas that goes through the inlet is supplied from the headspacer, then liner geometry makes no difference, because all the split does (I assume that you are splitting) is to sub-sample a portion of the sample to the column. If there is gas coming into the inlet from other sources (as it does with some set-ups and with all syringe injections) then there has to be time for the sample to mix with the other gas before it reaches the tip of the column. Assuming laminar flow the mixing has to happen by diffusion. Low MW carrier gasses mix very quickly, but I am not so sure about the compounds you want to see as peaks - I once got marginally better repeatability from syringe headspace when I moved the tip of the column down, and reduced the needle injection depth so that there was more space, and mixing time, between needle tip and column.

It would probably be quite straightforward to model it.

Peter

[Bigbear]

There shouldn't be. I use a 1mm liner for my P&T setup and split 150:1.