Multiple Headspace extraction using Agilent 7697A

[soccerdad007]

Hope everyone are keeping well in these strange times.

I am trying to develop a multiple headspace extraction method to measure caffeine in solids such as ground coffee.

Is there anyone out there doing MHE on an Agilent 7697A system as I would welcome any advice as to possible settings as part of the headspace parameters.

So far on one occasion I ran 5 extractions from a caffeine standard and got the expected results with the peak area of the caffeine decreasing according to the predicted Ln relationship. Since then I have run into problems and can't get things to work even when using the same conditions

Typically if I do 5 extractions from the same vial I only get peaks on the 5th run. If I do 3 extractions from the same vial I only get peaks on the 3rd run etc.

I have tried changing some of the settings in the headspace parameters such as the flow settings but without success partly as I am not totally sure of what each parameter does. I have spoken to Agilent but as this is quite an uncommon way of doing things they aren't too familiar with what I am trying to do.

Anyone able to help with some suggestions
Thanks
Kevin

[rb6banjo]

Good luck with that one. Over the years I've tried to get caffeine by GC with headspace SPME and nothing I've tried has worked reliably. I must admit, when the first things I tried didn't work right away, I gave up pretty easily. The GC would've been a backup method to what we normally use (HPLC).

[Gizmo]

Ditto on SPME GCMS for caffeine here - thought we might have nailed it down for a second using a C13 caffeine internal standard (which cost a bit), but Nah - back to HPLC

[James_Ball]

With a melting point of 235C I wouldn't think headspace would be a good method for Caffeine. It is very easy to extract with Dichloromethane or Ethyl Acetate though.