| The main components in edible oil are triglycerides.Fatty acids on triglycerides and their positional distribution,as well as trace non-triglyceride components in edible oils,present an important influence on the quality and nutritional value of edible oils.Some ingredients can also be used for adulteration analysis of edible oils.In the thesis,quantitative analysis of fatty acids and their different positions in edible oils was established using proton quantitative nuclear magnetic resonance spectroscopy(1H-qNMR)and carbon-13 quantitative nuclear magnetic resonance(13C-qNMR),respectively.The triglyceride sn-1,3 and sn-2 fatty acids in edible oil were analyzed by 13C-qNMR with an absolute method of quantitation,in which the 13C-qNMR spectra were processed by the data processing method of Lorentz/Gaussian ratio deconvolution integral.In addition,the solid phase extraction(SPE)technique and 1H-qNMR were combined to quantitatively analyze the non-triglyceride squalene in olive oil.(1).The 1H-qNMR method was presented for the determination of fatty acid content in edible oils using deuterated chloroform(CDCl3)as solvent,reference material benzoic acid as internal standard,zg30 pulse sequence,delay time(D1)=6s,number of scans(NS)=32.The experimental result showes that the mass ratio of fatty acid to benzoic acid is linear to the their NMR peaks area ratio.The intra-day RSDs of four fatty acids of linolenic acid(Ln),linoleic acid(L),oleic acid(O)and saturated fatty acids was 0.6%,0.2%,0.5%,and 0.7%,respectively.The detection limits(LOD)of linolenic acid,linoleic acid and oleic acid were 1.36 g/L,5.49 g/L and 4.86 g/L,respectively.The spiked recovery is between 98.86%and 101.9%.The result showes the method precision,good linearity,and reliable,which means that the 1H-qNMR method can be well used for simultaneously determining linolenic acid,linoleic acid,oleic acid and saturated fatty acid in edible oil.(2).A 13C-qNMR method was studied for the determination of fatty acid content in different positions in edible oil.The positional specificity analysis of sn-1,3 and sn-2 in fatty acids in edible oil was performed using reverse-gated decoupling spectrum with the pulse sequence as zgig30,the number of scans(NS)=256,and the number of sweeps(DS)=4.The NMR spectrum was determined by delay time(D1)=35 s,spectrum width(SW)=285 ppm,sampling time(aq)=2.3 s,center frequency(01P)=110 ppm.The direct normal integral,deconvolution integral using different Lorentz-Gaussian ratio,and other data processing methods were compared for the analysing the 13C-qNMR peaks.then the deconvolution integral with Lorentz-Gauss(3:2)was selected to extract the quantitative peak areas of two unsaturated fatty acids at sn-1,3 and sn-2,linoleic acid and oleic acid.The content of unsaturated fatty acids in different positions showed that the saturated fatty acids,sn-1 linoleic acid,sn-2 linoleic acid,sn-1,3 oleic acid,sn-2 oleic acid are:soybean oil(16.2%,30.4%,21.9%,13.6%,9.4%,(w/w,same as below);corn oil(15.3%,30.8%,20.5%,20.1%,13.3%);peanut oil(18.3%,18.7%,12.5%,24.9%,25.5%).The sn-1,3 linolenic acid,sn-2 linolenic acid in soybean oil are 4.5%and 4.1%,respectively,and they are undetected in corn oil and peanut oil.The result is corresponded with total linoleic acid and total oleic acid detected by above 1H-qNMR method.According to the 13CNMR,the position distribution of unsaturated fatty acids and saturated fatty acids can be analyzed.The method of using 13C-qNMR to analysis animal oil and vegetable oil is proposed,which provides a new idea for adulteration identification of edible oil.(3).A 1H-qNMR method for determinng squalene in olive oil was shown combined solid phase extraction(SPE).After the experimental conditions were investigated,the SPE conditions were selected as follows:silica gel SPE column,activated with 10 mL of n-hexane,loaded 1 g of olive oil dissolved in 10 mL of n-hexane,and eluted with 10 mL of n-hexane;the 1H-qNMR parameters were selected as:pulse sequence zg30,delay time(D1)=6 s,the number of scans(NS)=512.The result showes that the selected NMR quantitative peak area ratio of squalene to benzoic acid is linearly with their mass ratio.The inter-day RSD was 0.4%,the limit of quantitation(LOQ)was 3.26 g/L.The recovery rate was 100.3%during sample pretrement and 100.1%after sample pretrement. |
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