New Methods Of Detection For Fatty Acids In Vegetable Oil

In our daily life,there are many kinds of vegetable oil,such as rapeseed oil,soybean oil and peanut oil.However,the composition and content of fatty acids in vegetable oil are not same.In order to balance nutrition and reasonably ingest fatty acids in vegetable oil,developing a more simple and sensitive method for detecting fatty acids is essential.At present,the methods of detecting fatty acids in vegetable oil mainly include GC and GC-MS.These methods required triacylglyceride with high boiling point deriving into FAME with low boiling point before the analysis.This process produces a lot of by-products,and the derivatization reaction is not complete.In addition,the quantitative analysis of fatty acids in oils is based on the peak area normalization method.The method can only obtain relative content of fatty acids.In order to solve the problems of the traditional methods,through a series of optimization,methodological investigationand and verification experiments,we establish high performance liquid chromatography-evaporative light scattering detection method（HPLC-ELSD method）,high performance liquid chromatography-fluorescence detection method（HPLC-FLD method）and high performance liquid chromatography-laser induced fluorescence detection（HPLC-LIFD method）.The experimental results are as follows:The first part uses high performance liquid chromatography-evaporative light scattering detector method.Nine kinds of fatty acids achieve good separation by optimization of chromatographic conditions.And the linear relationship of fatty acids is good in this method.The relative standard deviation of stability and precision is within 3%.The minimum detection limit of erucic acid reach 10^-6 mol/L,and the minimum detection limit of other fatty acids reach 10^-5 mol/L.The average recovery rate is between 90%and 110%.In this method,the sample does not need to be derived and the absolute content of fatty acids in vegetable oil can be obtained.But this method only detects the fatty acids of C14-C22.In the second part,a fluorescent labeling reagent is synthesized,and EDC is used as condensing agent and DMAP as a catalyst to complete fluorescent labeling of fatty acids in 40 min at 35℃.When the fluorescence detector excitation wavelength was 440 run and the emission wavelength was 520 nm,the 19 kinds of fatty acids are separated well within 50 min by optimizing the chromatographic conditions.And the nineteen kinds of fatty acids in this method have a good linear relationship.The relative standard deviation of stability and precision are within 4%.The minimum detection limit of fatty acids reach 10^-8 mol/L.The average recovery rate of fatty acids are within 90%-110%.The method has a simple derivation process and can detect the fatty acids of C₃-C₂₂.Meanwhile,it has higher sensitivity than high performance liquid chromatography-evaporative light scattering detection method.The third part uses high performance liquid chromatography-laser induced fluorescence detection method.The diameter of the capillary column is 530 μm and the flow rate is 0.2 mL/min.Nineteen kinds of fatty acids are well separated through optimization of chromatographic conditions.The nineteen kinds of fatty acids in this method have a good linear relationship,and the relative standard deviations of stability and precision are within 3%.The minimum detection limit of eleven kinds of fatty acids reach 10^-9 mol/L,the minimum detection limit of eight kinds of fatty acids reach 10^-8 mol/L,and the average recovery rate of fatty acids are within 90%-110%.The method is simple to operate and has higher sensitivity than high performance liquid chromatography-fluorescence detection method.