Chemical ionization mass spectrometry of polyunsaturated fatty acids of human serum

Polyunsaturated fatty acids of human serum were analysed by combination gas‐liquid chromatography and chemical ionization mass spectrometry, using isobutane as the reagent gas. The method described yielded the molecular ion of long chain unsaturated fatty acids as the base peak; these were weak or unobservable in the corresponding electron impact mass spectra. In the chemical ionization mass spectromtery, the derivatization with trimethylsilyl ether was demonstrated to be useful for the location of the double bonds of unsaturated fatty acids. Applied to the serum polyunsaturated fatty acids, these methods have given identification of C 18:4 , C 20:4 , C 20:5 , C 22:4 , C 22:5 ω‐6, C 22:5 ω‐3, and C 22:6 .