Chromatography Forum

Are there new technologies that can speed headspace sampling? Has microwave or other new techniques been introduced into the market? Is it possible to reduce vial equilibration time to 10 minutes or better yet, 5 minutes or less? Thanks.

Very generally speaking, your GC cycle time will be the rate limiting step. Unless your GC run is less than 5 minutes total runtime you won't get any advantage from fast headspace extraction.
For example:
Our PE headspace samplers take the GC cycle time into account and can queue the vials in the sampler oven so that as soon as the GC is ready for the next injection the vial has equilibrated and is ready to inject. This means that the only 'long' equilibration time is for the very first vial. Even for short GC runs of around 2.5minutes.
I would think that most current manufacturers of headspace samplers have a similar feature.
Unless you're running isothermal, your GC cycle time will be (way) more than 5 minutes anyway.

I found that for residual solvents (I separated 18 solvents commonly used in 6 minutes) 10 minutes was more than enough time to perform headspace analysis. The key was to reduce sample size and improve partitioning of the solvents. I even did the 5 USP solvents (required at that time) in less than 2.5 minutes (unpublished work) runtime.

6 minutes was enough for non-alcoholic solvents, IPA in water required 8-10 minutes for best reproducibility but 6 minutes was acceptable.

If you are doing basic residual solvent analysis you should be able to meet your time goals. More than 15 minutes was counter productive in terms of reproducibility. I could do ppm to % levels of solvent in a 2% solution of 100µL of water or DMAc. Look up my paper in Analytical Chemistry in June of 1997 ( Anal. Chem. 1997, 69, 2221-2223 ) to see the recoveries of 18 solvents at 50 ppm in a 1 mg sample dissolved into 25µL of water/DMAc.

best wishes,

Rodney George
consultant

If you need really fast analysis you can always try the full evaporation technique where you heat a few uL of solution above the boiling point of the solvent. One minute is more than enough heating time when you use this technique.

Thanks for the tips. Analysis is for monitoring a reaction, so quick turn around time is key. Current method is 15 min headspace oven and 30 min GC. I am confident about reducing the GC analysis time. Not so confident about reducing the headspace oven time.

I have used the FET with other matrices before, but with straight sample, 0.02g, and usually higher levels of analytes. This analysis is for <1 ppm levels of ethylene oxide in surfactant. Do you recommend diluting the sample in solvent? Any recommendations on solvent? What kind of sample size?

TIA
Diane