References
Agren, J. J., Al-Amad, H., and Hanninen, O. 1991. Fatty acid content and composition of five fish species from the Persian Gulf. Comp. Biochem. Physiol. 100B 2 339-341. Aitzetmuller, K. 1975. The liquid chromatography of lipids a critical review. J. Chromatogr. 113 231-266. Alessandri, J.-M., Christon, R., Arfi, T. S., Riazi, A., and Leger, C. L. 1988. Comparative chromatographic study of modifications of brush-border membrane vesicles induced by an essential fatty acid-deficient diet. J....
F Kdu
Fats, see also specific fats , 168, 180, 181 GC analysis for peroxidation products, 232-233, 235 reverse-phase HPLC, 198-199 Fatty acid methyl esters FAMEs , 353-354 SPE by argentation chromatography, 33-34 Fatty acids HPLC analysis, 263, 274-275, 276 serum extraction, 274-275 sources, fatty acid composition, and TLC-FID response after hydrogenation, 67 SPE from brain extracts, 19 from cardiac tissue, 9, 18 from drinking water with porous carbon, 32 reverse-phase, 31 separation efficiency in, 9...
Triacylglycerols Eng
El Hamdy and Perkins 58,70 have reported the effects of changes in mobilephase polarity on the critical pair and other isomer resolution using a C18 column and a refractive index detector. Critical pairs, which result from the approximate equivalence of one double bond to a chain shortening by two methylene units, were effectively separated with acetone acetonitrile 63.6 36.4 as an isocratic mobile phase 70 . Other solvent systems are also capable of resolving critical pairs and triplets of...
Peak Quantitation
Quantitation of glycerolipid peaks is simple with detectors that give a reproducible mass or molar response. It is also helpful to have a sensitive detector response, which is linear over the working range for all analytes in the sample. None of the available detectors meet all these requirements fully, and a choice must be made in selecting the most appropriate detector for each application. Since natural glycerolipids usually do not contain chromophores, they are best detected by the...
Modified Folch Extraction
59 minimum sample biopsy required 0.2 g . Prepare the following solutions Solution A chloroform methanol 2 1 with 0.005 BHT v v w Solution B chloroform methanol 0.6 NaCl 86 14 1 v v v 2. Homogenize completely in at least 20 volumes of solution A 5 mL per 0.2 g , including appropriate internal standards 100 nmol di20 0 PC and di17 0 PE . 3. Add 1 mL of saline and vortex. 4. Separate the phases by centrifuging for 5 min at 1000 g or allow the phases to separate by letting them stand for 20 min...
Practical Applications
Practically no sample can be subjected directly to gas-liquid chromatographic analysis without a preceding isolation and purification procedure, except for some edible oils representing nearly pure triacylglycerol mixtures. All other samples must be extracted and the lipid extract purified from nonlipid contaminants. For the preparation of a total lipid extract, two classical methods have so far been used the method of Folch and co-workers 154 and the method of Bligh and Dyer 155 . Both these...
Alkylacetylsglycerols
This novel lipid class is an intermediate in the de novo pathway for biosynthesis of platelet activating factor PAF 69,70 and appears to possess independent biological activities 4 therefore, methods for analysis of this lipid subclass are very important. As with the diradylglycerols, there is a tendency for the sn-2-acetate group to migrate to the sn-3 position of glycerol, but this migration can be minimized by using boric acid-impregnated TLC plates for analysis 69 . Using a solvent system...
Monoradylglycerols
Free monoradylglycerols occur naturally to a limited extent and are generated by hydrolysis of lyso-GPL with phospholipase C 34 and by lipolysis of triacylglycerols with pancreative lipase 35 . Random generation of sn-1-, sn-2-, and sn-3-monoacylglycerols by Grignard degradation has been proposed for stereo-specific analyses of triacylglycerols 36 . For GLC the monoradylglycerols are converted into TMS or TBDMS ethers as described for diacylglycerols 30 . Other derivatives, such as acetates 24...
Applications of SPE to Separation of Lipid Species by Degree of Unsaturation
Argentation chromatography may be used to separate lipid materials on the basis of the number, type, and position of the unsaturated centers. Briefly, this type of chromatography takes advantage of the fact that compounds with ethylenic or acetylenic bonds interact weakly with silver ions. The nature of the interaction is not completely understood but appears to involve overlap of the olefin k-orbitals and the d- and -orbital of the silver ion. Steric factors affect the ease of overlap and the...
Iq 1
Typical gas Chromatograph of DMA and FAME derived from rat myocardium. a Ethanolamine glycerophosphates and b choline glycerophosphates separated using a polar phase capillary column and using a flame-ionization detector. 1, 16 0 DMA 2, 16 0 methyl ester 3, 18 0 DMA 4, 18 1 DMA 5, 18 0 methyl ester 6, 18 1 d7 methyl ester 7, 18 1 d9 methyl ester 8, 19 0 methyl ester internal standard used to check recoveries 9, 18 2 methyl ester 10, 20 0 methyl ester internal standard 11, 20 4 methyl ester 12,...
Bligh and Dyer Extraction
56 minimum sample required 0.15 g . Prepare a solution of chloroform methanol 1 2 with 0.005 BHT v v w . 2. Homogenize completely in 3 mL of the CHCl3 CH3OH with BHT solution, including appropriate internal standards 100 nmol di20 0 PC and di17 0 PE . 3. Add 0.8 mL of saline and vortex. 4. Separate the phases by adding 1 mL of chloroform, vortexing, and then adding 0.8 mL of saline and vortexing. 5. Centrifuge for 5 min at 1000 g or allow the phases to separate by letting them stand for 20 min...
Diradylglycerols Ypj
Nakagawa and Waku 79 have discussed the reverse-phase HPLC methods for the separation of alkenylacyl, alkylacyl, and diacylglycerols as the acetates. The solvent mixtures were acetonitrile 2-propanol methyl-t-butyl ether water 63 28 7 2 for the separation of alkenylacyl and alkylacyl analogs, and 72 18 8 2 for the separation of diacyl analogs. Peaks were detected by absorption at 205 nm. Choe et al. 80 have used the phospholipase C acetylation method for the characterization of long-chain...
Tridodecanoin Internal Standard
Temperature programming in GC, 117-119 HPLC, 197 programmed-temperature vaporization PTV injection, 107, 109 Testosterone, SFC analysis, 386, 392, 393 Thiazolidines, 229-233, 234 Thin-layer chromatography TLC , see also Chromarods , 300 applications, 301-307 to confirm SPE separation, 7 qualitative analysis, 124, 126-131 Thin-layer chromatography TLC FID detection after hydrogenation, 61-62, 67 applications, 63-69 equipment, 51-52 method and optimization, 52-55 outlook for, 69-71 peak...
Complex LipidClass Separations
More complex lipid separations are also possible on silica SPE columns. Moser et al. 1981 obtained four fractions of increasing polarity from plasma lipid extracts that had been subjected to alkaline methanolyis to release the fatty acids from the triglycerides and glycerophospholipids. The first fraction, eluted with hexane benzene, contained fatty acid methyl esters FAMEs and unhydrolyzed cholesterol esters. Components eluted with chloroform in the second fraction were not identified. The...
Derivatization
Gas chromatography GC is an excellent tool for lipid analysis and offers the ability to quantitate and characterize lipid species of interest. GC protocols usually require the derivatization of lipid molecules to polar groups and the removal of reactive hydrogens. Derivatized lipids are less polar and are more easily volatilized, and thus more suitable for GC analysis. There are many protocols for preparing lipids for GC. Proper derivatization techniques should be chosen to optimize final data....