| The similarity and variety of triacylglycerols(TAGs)results in the complexity present in natural oil samples,and make the complete analysis of TAGs a difficult and challenging task.In the thesis an effective method for separation,identification,and quantification of TAG components in edible oils by LC-MS using a porous graphitic carbon(PGC)column combined with a toluene-isopropanol mobile phase system was proposed.A new efficient and rapid method was provided for authentication of edible oils,based on the studies on discrepancies in components of TAGs in different edible oils.The main work includes two parts below:(1)A novel and practical method of separating and analyzing triacylglycerol(TAG)in edible oil by using high-performance liquid chromatography(HPLC)coupled with atmospheric-pressure chemical ionization(APCI)mass spectrometry(MS)using a porous graphitic carbon(PGC)column(150 mm×2.1 mm,5 ?m)and a toluene–isopropanol–formic acid gradient mobile phase was established.After systematically investigating the impact of experimental conditions on retention and separation of TAG components,the gradient toluene–isopropanol mobile phase containing 0.1% formic acid changing from 50:50 to 80:20in 30 min was presented.The column temperature was set to 35 °C.The flow rate was set to0.3 mL/min.Sample concentration was 0.08 mg/mL.Injection volume was 10 ?L.APCI-MS was used under positive-ion acquisition mode.Under the presented experimental conditions,the TAG retention displayed a special order and was summarized to fit as follows: S-ECN(special equivalent carbon number)= 2CN(carbon number)-3DB(double bond number)-5uFA(unsaturated fatty acid number).TAGs were eluted in ascending order of S-ECN.Then,PGC LC-APCI/MS method was applied to separate TAGs in six vegetable oils,resulting in the recognition of 27,21,22,28,25 and 31 kinds of TAGs in corn oil,olive oil,sunflower seed oil,soybean oil,sesame oil,and peanut oil,respectively.The separation and identification of TAGs in edible oils through PGC LC-APCI/MS method was rapid,reproducible,and durable.(2)TAG compositions in 16 kinds of edible oils,including 12 kinds of vegetable oils and4 kinds of animal fats,were further separated and analyzed using above PGC LC-APCI/MSmethod,Apart from the six vegetable oils that has been profiled in part(1),14,23,18,22,23,26 kinds of TAGs in amygdalus pedunculata pall oil,canola oil,grape seed oil,wheat germ oil,rapeseed oil,and rice bran oil,respectively,were detected and identified.TAG compositions in lard fat,chicken fat,mutton fat,and butter were also analyzed and compared.The separation ability for some TAG regioisomers of sn-2 and sn-1/3 position using the presented PGC LC-APCI/MS method was studied,and the experimental results revealed that regioisomers of OOP/OPO,SOS/SSO,and SOP/SPO can be separated by the method.Consulting from the references,the PGC LC-MS method has been applied to the detection,identification and quantification of TAGs such as LLnLn,LLLn,LLL,OLL,OOL,OLLn,PLL,OOO,POL,OPL,POO,SLL,SOL,BOL,SPO in corn oil,soybean oil,peanut oil,lard fat,and chicken fat,respectively,using the similar calibration curves of alternative TAG standards.Finally,the statistical evaluation of the TAG profiles from the total 58 oil samples was conducted on the basis of principal component analysis(PCA)by MetaboNexus,and orthogonal partial least squares-discriminant analysis(OPLS-DA)by SIMCA-P was proceeded with chromatographic data of corn oils,soybean oils peanut oils sunflower seed oils and rapeseed oils.The results showed the clear discrepancies among different clusters of oil samples,and the TAG markers between corn oil,soybean oil,sunflower seed oil,respectively,and other edible oils were found.The research provides new practices for the analysis TAGs and adulteration authentication of edible oils. |
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