Chromatography Forum

Got a quick question. I know increasing oven temperature in a headspace analyzer increases sensitivity (there are other factors involved), I was wondering if it would effect retention time as well? Just getting curious results after increasing the oven temp on my headspace, any insight would be great!

FYI, its a HP 6794 headspace analyzer with a 6890 GC/FID. I am quantifying terpenes in hops. Let me know if you need to know anything else. Thanks!

In theory, merely heating the sample to a larger temperature should not have an effect on the RT on a specific column under a specific set of chromatographic conditions. Does that sampler perform a pressurized injection or is it atmospheric pressure? Are you seeing major shifts in RT? If yes, it might be indicative of a change in the flow-rate through your system. If you have a large concentration of some solvent in your sample (e.g., ethanol in an alcoholic beverage), putting more ethanol on the column might have an influence on how your analytes are refocussed at the head of the column after injection. I would still not expect RT's to change dramatically. I have known some folks who have somewhat unrealistic expectations for the reproducibility of RT's.

If you are using a low split ratio you can easily get retention time shifts with concentration changes. Make sure you're using an adequate split ratio (we typically run 25:1). It is counterintuitive, but higher split ratios with gas phase injections will many times lead to greater sensitivity (better chromatography).