Hello everyone,

In case anyone is interested in this post about GC of
FAMEs and hasn't seen it, I'm copying it to the group.
___________________________________
From the St. Louis Chromatography Discussion Group
(http://www.stlcdg.org/wwwboard/messages/2222.html)
Hans Mueller writes about 'Transesterification with TMSH' :-

Having posted the following message in another forum about a week
ago, without response, there should be an increased chance to find
someone with answers by reposting it here:
Some years ago (J. Chromatogr., 228, 75 (1982)) we tried some highly
touted reagents for methylating fatty acids in the GC injector. It
turned out that we obtained transesterification of inadvertently co-
extracted lipids, as well as ghosting via transesterification of such
lipids which had deposited in the injector. Since then we have
judicially avoided such reagents.

Recently, trimethylsulfonium hydroxide (TMSH) has strongly been
recommended for transesterification of lipids in the injector. I am
still skeptical.
Therefore, it would be highly appreciated to get some information
from someone who criticaly looked at the scope of this reacion.
Some questions: Do lipid deposits, which will form if the reaction
does not proceed 100%, react with subsequent injecions of TMSH (only
clearly visible if no lipids are coinjected)?
Does cholesterol of cholesteryl esters react with TMSH and then
interferes in the FAME chromatogram? Ditto for glycerol of
triglycerides, etc...?
Is methylene formed which reacts with double bonds?
On what criteria is quantitative repeatability based?
About how many injections are possible before the column deteriorates
(I can not believe that some reagent does not enter the column)?

PS: in the meanwhile I found one example of an article
about a problem through interference by hydroxy fatty acids: Vosmann,
et al, Lipids, March 31:3, 349 (1996) + a hint of a caution on the
web site, http://www.lipid.co.uk/infores/lit_surv/ext_meth.html

(There is also a reply to this post from Ralph Calvert on the same
page)

___________________________________
Best wishes
Jo

P.S. We now have 23 members of 'lipids'.
P.P.S. If there are any interesting lipid websites you feel
should be linked to the eGroups website, and aren't, let me
know and I'll add them (or if you register with egroups you
can do this yourself).

http://www.egroups.com/group/lipids
(click on 'links' in the menu to view listed websites)