lipid analysis by UPLC-MS or GC-MS? How to choose?

[guira]

Hi all
I'm analysing lipids in (really) fatty tissues. To do it, i do a first lipid extraction using chloroform. As lipids are not soluble in acetonitrile:water mixtures I need to dissolve them in chloroform solutions.
Now the point is.. what's next? Is is possible to do a RP-UPLC-MS analysis using a methanol:chlroroform solution as sample solvent or that will destroy the columns and split the peaks?...

Maybe it'd be better to derivatize and use GC-MS??

[Ron]

There is a lot of literature on the analysis of lipids by LC and LCMS. Try contacting the manufacturer of your LCMS and see if they have any applications notes for this application on your configuration. A quick internet search will probably generate hundreds of references for this type of analysis.

Lipids are not often done by GCMS unless they are very small.

[RAD]

are you analyzing intact lipids or the fatty acids attached to the intact lipids?

[guira]

That's the point. I'm focusing on the intact lipids, that's why I don't know if GC would be a better choise, or even if it's possible to do it by RP-LCMS

[RAD]

Intact lipids are much better done by LC than by GC.
It can be done by GC but I think you would be much better off using LC

There are many protocols to analyze phospholipids by LC but if you are looking at neutral lipids as well as phospholipids it is a little more difficult.

Are you looking at all lipids or just phospholipids?

[Ken]

Hi there, there are a lot of works currently done analyzing lipids using LCMS/MS rather than GC/MS based instrumentations.

The more reason for you to use LCMS/MS since you wanted to analyse intact lipids - with GC, the EI will caused fragmentations on your samples hence it's not advisable to use GCMS or GCMS/MS instrumentations for intact lipid analyses.

As you have mentioned, once you have used chloroform as your solvent; try converting back to higher polarity by a mixture of DCM, ACN or methanol ^^

I've done lipid analyses and profiling works using HPLC-MS/MS works; so ^^ let me know if you need more advise ^^

Cheers ~

[wilsontrace1]

Hi,
As per my suggestion, lipids can be analyzed in a better way using GC/MS. It specifically helps in structure determination of unknown organic compounds in complex mixtures with a greater sensitivity and offers a better resolution.
To perform the data processing steps after experimentation, try using SimLipid from Premier Biosoft - http://www.premierbiosoft.com/lipid/index.html
Cheers !!

Wilson

[Peter Apps]

Hi Wilson

Welcome to the forum. Sorry to disagree with you on your very first post, but intact lipids are a real challenge by GC, mainly because their high molecular weights mean that they have very low vapour pressures and getting them into the gas phase so that they can be chromatographed requires temperatures at which they are vulnerable to thermal decomposition.

Do you by any chance work for Premier Biosoft ?

Peter

[Consumer Products Guy]

We've done intact triglycerides by high-temperature GC using a specialty 10m thin-film metal capillary. We've also used HPLC.