GC Analysis of Triglycerides

[okay]

Is it possible to analyze triglycerides without breaking them down into FAMEs? Currently, I am adding MSTFA to my sample to undergo silyation. But, the triglyceride and diglyceride peaks are very broad. Does this make sense?

Thanks!

[chromatographer1]

Yes it makes sense.

Would you expect a C60 peak to be broad in your GC configuration?

How many carbons are in your triglycerides?

Any questions?

Rod

[Consumer Products Guy]

Is it possible to analyze triglycerides without breaking them down into FAMEs? Currently, I am adding MSTFA to my sample to undergo silyation. But, the triglyceride and diglyceride peaks are very broad. Does this make sense?

Thanks!

We use a metal capillary column designed for high temperatures for intact triglycerides analysis. This column (see Quadrex, Phenomenex, maybe Restek, others) is like 10 meters and has a thin film dimethylsiloxane. Fused silica breaks down at high temperatures.

Of course the MSTFA will not react with triglycerides, only mono and di, and any free fatty acids.

[okay]

thanks for your feedback!

I'm not sure how many carbons are in the triglycerides. My sample is lipids extracted from algae...I'm actually following an ASTM method (d6584) for determining total mono, di, and tri-glycerides in biodiesels. Except I am not testing for methyl esters (no esterification)...

I've tried looking it up, but why doesn't the MSTFA modify the triglycerides?

[chromatographer1]

The reagent reacts by replacing a reactive hydrogen on the molecule, as in hydroxyls and acids.

It does not break open and react with an ester.

Rod

[chromatographer1]

Most common triglycerides are glycerin = 3 carbons, and 3 x a C18 fatty acid, or 54 carbons.

Thus, 57 carbons, in a large three dimensional molecule.

If your C18 FAME elutes in 10 minutes, when will the C57 triester elute?

Rod

[Consumer Products Guy]

You can buy triglyceride standards from NuChek Prep, like 18-18-18.