Hello,

Unfortunately and as I have heard from experts , headspace is not very "quantitative". Some might oppose and do not like it, but with limited experience could not agree more with the lack of quantitation issues.

Solution is: you need to develop good internal standards (10s-100s) of authentic commercially purchased chemicals and find their RSDs/ CVs for system suitability as QCs/QAs before relying on any quantitative results. The confidence intervals will dictate the quantitative results for further analysis/ trust. It's not the GC (chromatography) to blame, but the "headspace" it self, the volatility, the matrix effects, gas syringes, carry overs etc. are big issues, that are further compounded with FID issues.

Also, FID has lots of inconsistency issues (c (can not detect co-elutions, IDing without standards is next to impossible). Switch to GC-MS is possible for better ID and Rt matrices for data acquisition/ downstream IDing.

May be more experts will chime in with better answers and guidance too. Let's wait.

Thanks,

Hi.

Personally, I was never able to reproduce areas with headspace manual injection and FID as detection. If can get an auto-sampler, or develop a trap method it will be better. Nevertheless, I would strongly recommend you to go for SPME. You can keep manual operation and it will (almost surely) fix your issues with reproductability.

Cheers!

So, what I can say - it is very easy to get good results. I've used it for years.

The thermostatting of sample must be minimum 30 minutes. The vial/cap must be leak free(you can capp a 10 mL of methanol and control the weight change during 1hour).

If you make all steps same in same time - it must work.

To improve the reproducibility you can use an internal standard.

Most of my Students get (4 point calibr. curve) R2>0,990 after short tutorial.

Regards

GB