Application And Determination Of Residual Glyceride In Biodiesel By Thin Layer Chromatography-gas Chromatography

Residual glyceride in biodiesel will seriously affect the engine performance and shorten the life of the engine,its presence is considered undesirable in biodiesel products.Therefore,it is requested to develop a practical method to determine the residual glyceride in biodiesel.In this thesis,a method to determine residual glyceride in biodiesel was developed on the basis of thin layer chromatography-thermally assised hydrolysis and methylation-gas chromatography(TLC-THM-GC).At first,a method of thin layer chromatography(TLC)was developed to separate residual glycerides such as monoglyceride,diglyceride,triglyceride,and fatty acid methyl esters which were the main composition of biodiesel.The residual glycerides were well separated by TLC on silica plate with toluene/acetone = 92/8(V/V)as developing solvent.The Rf of monoglyceride,diglyceride,fatty acid methyl esters and triglyceride were 0.06,0.40-0.55,0.83 and 0.92,respectively.Secondly,in order to obtained the high yield of methyl derivatives of fatty acid formed from the thermally assised hydrolysis and methylation of glyceride by THM-GC,two important facters snch as reaction temperature and the kind of derivative reagent were examed.The obtained results showed that 0.1 mol/L trimethylsulfonium hydroxide at 350 ? enabled highly sentsitive determination glyceride.Thirdly,a method of THM-GC was applied to determine monoglyceride,diglyceride and triglyceride in biodiesel,which were separated by TLC.Samples were separated,the separated components were extracted,and diluted to a given volume.3?L sample was injected into a sample cup,3 ?L TMSH(0.1 mol/L)was added also as methylation reagent.Then the samples was determined by THM-GC.The calibration curves of monostearin(C18:0),distearin(C18:0),tristearin(C18:0),diolein(C18:1),dilinolein(C18:2),dilinolenin(C18:3)exhibit good linearity with the regression coefficients from 0.9863 to 0.9993 at the concentrations from 60 to 2000 ?g/mL.The reproducibility was farily good with the RSD(n=5)from 3.2%to 7.2%for four kinds of diglycerides at 250 ?g/mL concentration level.The potential of the proposed method was assessed by applying it determination glyceride in biodiesel samples.The results prove that TLC-THM-GC is an accurte and highly sentsitive method for determining not only residual glycerides but also each fatty acid contained in glycerides for biodiesel samples.Lastly,the reasons of small response value of polyunsaturated fatty acid glyceride by TLC-THM-GC were studied.One of the reasons is the slight isomerization of linolenic acid methyl ester occurred in the step of derivatization.Another reason is lower extraction efficiency of C18:3.from silica plate.The conclusion is that the quantitative determition of glyceride containing the polyunsaturated fatty acid need to be corrected.