Separation and identification of unsaturated fatty acid isomers in blood serum and therapeutic oil preparations in the form of their oxazoline derivatives by GC-MS

Fatty acids from blood serum lipids and fish oil preparations are derivatized with 2-amino-2-methyl-1-propanol to form 2-substituted 4,4-dimethyloxazolines. The derivatives are separated on a 25 m × 0.25 mm FFAP column and identified by mass spectrometry using electron impact ionization. The positions of the double bonds of mono- and polyunsaturated fatty acids can be easily and reliably recognized from a characteristic fragmentation feature of the oxazolines. Several unsaturated C16 to C22 fatty acid isomers are identified whose exact structure has not been derived from the commonly used methyl esters.