Optimization And Application Of Aquatic Fatty Acid Determine By Gas Chromatography

Currently, fish muscle and freeze-dry rotifers fatty acid determination were little researched, and determination of fatty acid is an important indicator of the study in rotifer and fish. Effects of lipids extraction, extraction solvents and different mixing proportion on fish muscle and freeze-dry rotifers (Brachionus rotundiformis) were studied. In addition, the effects of different temperature program on the determination results, effects of derivatization reagent, the derivatization reaction time and temperature on the GC determination results were also studied. The optimized method were used in the determination of five kinds of fish(Silurus soldatovi, Amur Sturgeon, Thymallus arcticus grubei, Esox reicherti and Hypomesus olidus) in northeast region to determine the fatty acid. It provided a reference for nutritional assessment.Three extraction solvents were designed, chloroform:methanol (2:1,1:1,1:2), benzene:petroleum ether (2:1,1:1,1:2), acetone:petroleum ether (1:4,3:7,2:3), to extract fish muscle and freeze-dry rotifers lipids with1-3times extraction, the lipid content and saponification numbers were determined and were compared with Soxhlet extractor method (national standard), screening come to the best ratio of three kinds of extraction solvents.Select the best solvent for the fish muscle and the rotifer fat extraction, and use five different derivative solvent (10%sulfuric acid-methanol solution,0.4mol/L potassium hydroxide-methanol,10%sulfuric acid-methanol solution and0.4mol/L potassium hydroxide-methanol solution of10%sulfuric acid-methanol solution and14%boron trifluoride-methanol solution,0.4mol/L potassium hydroxide-methanol solution and14%boron trifluoride-methanol solution) to conduct the derivative reaction. Set three different reaction time (5min,10min and20min) and three different reaction temperature (40℃,50℃and60℃), filter out the best derivative conditions of fish muscle and rotifers and summarized the appropriate method for the determination of fat acids of fish muscle and the rotifers. Finally determine the fatty acids of the five kinds of fish(Silurus soldatovi, Amur Sturgeon, Thymallus arcticus grubei, Esox reicherti and Hypomesus olidus) in northeast region with the best method.Results indicated that:the extracting times did not significantly (P>0.05) affect lipid content in all treated groups, and optimum solvent proportions of fish muscle were chloroform:methanol(2:1), acetone:petroleum ether(2:3) and Soxhlet extractor method (national standard). The lipid content and saponification number of chloroform:methanol(2:1)treatment were12.09%and179, respectively, and were significantly (P<0.05) higher than that of Soxhlet extractor method (national standard) and other treatments, so the best extraction solvent and matching of fish muscle was chloroform:methanol(2:1); optimum solvent proportion of freeze-dry rotifers were chloroform:methanol(2:1), benzene:petroleum ether(1:2)and acetone:petroleum ether(2:3). The lipid content and saponification number of acetone:petroleum ether(2:3) treatment were9.71%and198, respectively, and were significantly (P<0.05) higher than that of Soxhlet extractor method (national standard) and other treatments, so the best extraction solvent and matching of freeze-dry rotifers was chloroform: methanol(2:1). In this study, the best temperature program was got after optimization. It was that initial temperature at150℃(hold for3min) rose to200℃(to maintain2min) by rate of5℃/min, then rose to230℃(hold for15min) by rate of2℃/min. The best derivative of conditions of fish muscle was as follows. The best derivatization reagent was10%sulfuric acid-methanol solution and0.4mol/L potassium hydroxide-methanol solution, the best reaction time was10min and the optimum reaction temperature was50℃. The best derivative of conditions of freeze-dry rotifers was as follows. The best derivatization reagent was10%sulfuric acid-methanol solution and0.4mol/L potassium hydroxide-methanol solution, the best reaction time was20min and the optimum reaction temperature was60℃. The new optimization method can save more time than Soxhlet extractor method (national standard), simplifies the experimental operation and improve the efficiency of the test. In addition, the unsaturated fatty acid content of the determination of fat acids of the five kinds of fish (Silurus soldatovi, Amur Sturgeon, Thymallus arcticus grubei, Esox reicherti and Hypomesus olidus) was high, which had a great development potential and economic value.