Identification And Analysis Of Fatty Acids In Inferior Edible Vegetable Oil By GC/MS

Nutrient composition of edible vegetable oil is composed of saturated and unsaturated fatty acids esters containing carbon 18 to 22. Some of the polyunsaturated fatty acids such as linoleic acid and linolenic acid are essential fatty acids and take on the important physiological functions. Therefore, when the quality of the oil changes, the kinds and content of the fatty acid may change. This experiment adopts the method of gas chromatography mass spectrometry to identify and analysize the kinds of fatty acids and contents of inferior edible vegetable oil. Part 1 Identification and analysis on short chain fatty acids of edible vegetable oil in GC/MSObjective: Using gas chromatography – mass spectrometry(GC/MS) to analysize the kinds and content of short chain fatty acids which produced by the heated sample of edible vegetable oil.Methods: It can be a saponification reaction between long chain fatty acid ester and sodium hydroxide. Then take the aqueous phase to acidize, the short chain fatty acids are dissociated. The short chain fatty acids was extracted by n-hexane and detected by GC/MS.Results: By GC/MS detection, total ion flow mass spectrum of oil sample has been gained compared with the standard spectrum, the oil sample which has been heated contains caproic acid, heptylic acid and octanoic acid. Between 100℃~250℃,with the gradual rise of heating temperature, the amount of short chain fatty acids also increase gradually.Octylic acid content is highest among them. In the range of linearity, they have a good relativity and the limit of detection(LOD) is 2.73×10-3μg·mL-1,4.07×10-3μg·mL-1,2.33×10-2μg·mL-1 and the recovery rate is 94.4~102.7% and RSD is 1.9%,2.6%,2.7% respectively.Conclusion: This method is simple and has a great systematic suitability which is expected to be a method for identification of inferior edible vegetable oil. Part 2 Compare the difference between edible vegetable oils and animal oils by GC/MSObjective: Find the difference of the fatty acids between edible vegetable oils and animal oils by the qualitative analysis in GC/MS.Method: It can be a reaction between the oil and 2%NaOH-CH3 OH and 14%BF3 and produce fatty acid methyl ester(FAME) by the method of heat, condensate and reflux. Fatty acid methyl ester was extracted by n-hexane and detected in GC/MS.Results: The mass spectrum shows that vegetable oil and animal oil has a obvious difference in the kinds of fatty acids. Animal oil contains less than 12 carbon saturated fatty acids and the kinds of saturated fatty acids is various. The kinds of fatty acids of vegetable oil were less than animal oil and vegetable oil contains few saturated fatty acids which is the odd number, branch or below 16 carbon atoms.Conclusion: The method of fatty acid methyl ester is simple and rapid, and has a great applicability. It can be used to identify the inferior oil,especially the oil which was mixed with animal oil or refined by the cooking oil after eating...