Transesterification of phospholipids or triglycerides to fatty acid benzyl esters with simultaneous methylation of free fatty acids for gas-liquid chromatographic analysis.

A novel method is presented for transesterification of fatty acid esters in phospholipids and triglycerides to benzyl esters while simultaneously recovering free fatty acids as methyl esters. Transesterification is catalyzed by 0.2 M (m-trifluoromethyl phenyl)trimethyl ammonium hydroxide in methylene chloride, 10% (v/v) benzyl alcohol, and 1% (w/v) potassium tert-butoxide, and is complete in 30 min at room temperature. Methyl esters of all common fatty acids separate from the benzyl esters formed from phospholipids. This method has broad utility and is applicable to the formation of esters optimized for detection by absorbance or fluorescence (high performance liquid chromatography), electron capture (gas-liquid chromatography), or negative ion chemical ionization (gas-liquid chromatography-mass spectrometry).