Alkyldimethylaminoethyl ester iodides for improved analysis of fatty acids by electrospray ionization tandem mass spectrometry

The development of a new class of derivatives, the alkyldimethylaminoethyl ester iodides, for the analysis of fatty acids by electrospray ionization tandem mass spectrometry is described. They are prepared by quaternization of dimethylaminoethyl esters with alkyl iodides. The trimethylaminoethyl (choline) ester iodide affords between 8 and 12 times greater signal intensity than the corresponding dimethylaminoethyl ester used in the analysis of long to very long chain fatty acids in plasma samples. It is a superior derivative for unsaturated and monohydroxylated long chain fatty acids but unsuitable for bile acids and dicarboxylic acids.