Short chain fatty acids in urine

[PEfan]

Hello,
I am measuring short chain fatty acids in urine. Does anyone there have experience with it? What technique is best to measure them?
Thanks.

[Davide]

I have an experience in the measuring free fatty acid in water with a GCMS and a DB-FFAP column (30 m 0.25 mm). May be you can assimile urine as a water sample.

[PEfan]

Could you tell me what method you use to introduce the sample to the GC? I have the FFAP column in place, and I have been trying headspace, TD and SPME but none of them seem to detect the SCFA present in urine. Maybe I am missing something.
Thanks a lot for your help. Much appreciated.

[chromatographer1]

Your SCFAs are most likely present as the salt form in urine. Salts have very little volatility and you are unlikely to separate them from an aqueous solution.

Perhaps if you acidified the urine sample, lowering the pH, tying up all the bases in urine and reducing the volume of sample in your headspace vial, you might achieve success. However,

I suspect you may wish to use a precolumn and inject the sample directly for better results. A packed injection liner, packed with quartz wool might be a place to start. On column might be better with of course a guard deactivated column ahead of your analytical column.

There is literature on this. Look in medical analytical journals.

Good luck.

Chromatographer1