Chromatography Forum

So I have run several GC analyses of human plasma extracts, and I continue to see a large peak occurring after C12:0 and before C14:0. I have reviewed the literature and found very little about unsaturated lauric acid content in human plasma so I would be surprised if this peak (roughly 22% of total Fatty Acid Content) fell within that category. I'd rather not have to order another standard only to find that it also does not match this peak. Has anyone experienced something like this?

I guess you're not using a mass spectrometer as your detector. That'd be my first suggestion. Find someone who has a mass spec. and can look at your sample to see if it's really a fatty acid derivative (I presume that you're derivatizing them before the analysis). Is it possible that it's something else? How selective is your extraction/derivatization procedure for fatty acids?

I'm a polymer/coatings guy so please excuse my ignorance of your problem.

Maybe the extraction/derivitization are not as specific as I thought, and I am currently using only FID detector. Thanks for your advice I plan to follow up on this post next week when I get a chance to use GC-MS.

I don't know your preparation method or your GC column - but would cholesterol make sense?

Cholesterol and similar stuff requires significantly higher temperatures to elute than fatty acids (unless he's using uncommon derivatization technique).

We most often do fatty acid methyl esters here, but have done some trimethylsilylation of them as well. Sometimes, well-documented artifact peaks can show up with TMS derivatization, readily identified if GCMS is used.