Extraction of Channel Catfish Muscle Oil by Supercritical Carbon Dioxide and Determination of Fatty Acids by Gas Chromatography-Electron Ionization-Mass Spectrometry
A novel method was established for the qualitative and quantitative determination of fatty acids in Channel Catfish muscle by gas chromatography-electron ionzation-mass spectrometry (GC-EI-MS) after super-critical carbon dioxide fluid extraction (SFE-CO(2)). The extraction parameters for the methodology were optimized. The optimal conditions were extraction pressure of 25 MPa at 45 degrees C and extraction time of 100 min at the rate of carbon dioxide 30 L/h. The fatty acids in the muscle oil were derived by boron-trifluoride method. The saponification time was 10 min, and the esterication time was 20 min. The obtained fatty acid methylesters were separated by gas chromatography using a HP-Innowax capillary column, and were detected by electron ionization mass spectrometry. Full scan mode and SIM mode were used for the qualitative and quantitative analysis, respectively. In the SIM mode, saturated fatty acids were determined with m/z 74, mono-unsaturated fatty acids were determined with m/z 55, double-unsaturated fatty acids were determined with m/z 67, and polyunsaturated fatty acids were determined with m/z 79. The detection limits of 14 fatty acids were 2.2-20.0 mu g/L (S/N = 3), and the quantitative limits were 7.39-59.85 mu g/L (S/N = 10). The recoveries fell in the range from 90.0% to 111.2% (n = 4), and the relative standard deviation was between 2.0% and 5.9%. This effective, sensitive and reproducible method can be used for the determination of fatty acids in Channel Catfish muscle sample.