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)?