Abstract: A simple and sensitive method for the determination of fatty acids in Alaska deep-sea fish oil using 1-[2-(p-toluenesulfonate)-ethyl]-2-phenylimidazole-[4,5-f]-9,10-phenanthrene (TSEPIP) as derivatization reagent on a reversed phase Eclipse XDB-C8 (4.6×150mm, 5μm, Agilent) column in conjunction with a gradient elution followed by reversed phase high-performance liquid chromatography with fluorescence detection at 380 nm(excitation wavelength 260 nm) and tandem mass spectrometric identification has been developed. The contents of 26 free fatty acids in deep-sea fish oil were determined by external standard method, and the linear range of them was 200.0 pmol～48.83 fmol, all the correlation coefficients>0.9996, detection limits were 3.824～47.13 fmol (at signal to noise 3:1, S/N 3:1). The identification of all saturated and unsaturated fatty acid derivatives was carried out by post-column tandem mass spectrometry with atmospheric pressure chemical ionization (APCI) source in positive-ion mode, and the relative content of all saturated and unsaturated fatty acids was contrasted by peak area. According to the analysis of HPLC/MS/APCI, 25 fatty acids were identified, the main fatty acids in deep-sea fish oil are C12～C22 and 69.71% (peak area percent) of them are unsaturated fatty acids, especially polyunsaturated fatty acids which have important physiological function, such as 5, 8, 11, 14, 17-eicosapentaenoic acid(EPA, 16.62%), 2, 5, 8, 11, 14, 17-docosahexenoic acid (DHA, 12.31%).

Key words: Alaska deep-sea fish oil, HPLC-MS/MS, pre-column derivatization, fluorescence, fatty acids