Chromatography Forum

I know that you can adjust the GC side to obtain a desired "split ratio"; but how much vollume is injected to the GC inlet from the headspace tubing as a vaporized mass from the sealed crimped 20 mL vials?
I need to know this in order to know how much is ultimately put 'on-column".

It depends upon whether you are using a fixed loop injector (Agilent) or a timed flow injector(PE).

The wt of sample on column cannot be determined. The volume on-column can be.

Volume equals the volume of the loop at the pressure used at equilibrium (usually 1 atmosphere absolute - 14.7 psia) corrected by the pressure of the sample as it is split in the injector (at 2 atmospheres absolute - 29.4 psia, the volume is 1/2 of the volume at 14.7 psia) divided by the split ratio.

The timed injection volume is calculated by the time the injector is on times the flow rate minus the amount of dead volume between the injector valve and the end of the transfer line if a split injector is used. Then the amount is divided by the split ratio.

The amount of the weight of sample injected depends upon the weight of the sample per volume in the headspace vial at 1 atmosphere. And that can only be compared to a direct injection without a split being used of a known volume of a known concentration.

best wishes,

Rod

So, given all of what you've said, what difference does all of that make? At this point we only want to see if the volume transferred can be increased from 1 mL of vapor.

It makes a lot of difference. But it is too big a topic to discuss on the forum.

Since I still don't know what type of injection you are making from your headspace vial, yes, you can get a larger loop or time inject for a longer time. You can get more sample volume.

If that larger volume succeeds in improving your sensitivity of your analyte analysis is another question which answer you may not like.

best wishes,

Rod