Showing papers in "Lipids in 1966"

Quantitative analysis of phospholipids by thin-layer chromatography and phosphorus analysis of spots.

Abstract: Quantitative Analysis of Phospholipids by Thin-Layer Chromatographyand Phosphorus Analysis of Spots p ROCEDURES FOR ANALYSIS of phospholipid composition by thin-layer chromatography (TLC) and phospho~nts analysis have been reported from a number of laboratories. These procedures usually depend upon one-dimensional TLC and elution of spots before analysis. The method reported here has the advantage of improved separations by two-dimensionM TLC, direct aspiration of spots by suction, and phosphorus analysis without pr ior elution. Our procedure depends upon two-dimensional TLC with the solvent pairs 1) chloroform/ methanol/water 65/25/4 a~ld n-butanol/acetic acid/water 60/20/20; and 2) chloroform/ methanol/2S% aqueous ammonia 65/35/5 followed by chloroform/acetone/methanol/acetic acid/water 5/271/1/0.5. The adsorbent composed of silica gel plain/magnesium silicate 9/1 (1) after spreading with a conventional Desaga spreader (0.25 nnn layer) is heat activated for 20 rain at 120C, cooled for 30 rain, spotted, and ehromatograms developed in chambers lined with solvent-saturated paper (2). Spots are detected by spraying with a 0.6% solution of potassium dichromate in 55% (by wt) sulfuric acid followed by heating for 30 rain at 180C in a forced draf t oven or by exposure to iodine vapors. Af ter development, spots are circled and lettered for identification and several blank areas corresponding in size to the sample spots are marked off. A typical ehromatogram of each series is photographed (Polaroid camera) and the spots recovered by aspiration. Aspirat ion of the spots directly into 30 ml Xjeldahl digestion flasks is accomplished by fitting a rubber stopper with two plastic tubes removed from plastic wash bottles. One tube with a pointed end serves as the intake and the other tube for attachment to a water pump for suction. Adsorbent is prevented from passing out of the digestion flask during aspiration by adding 0.9 ml of 72% perehlorie acid (used subsequently for digestion) to the flask to act as a liquid t rap by moistening the lower bulb portion of the flask and by insertion of a 1 cm square of \"Kimwipe\" or similar light weight paper into the end of the suction tube to serve as a filter. After aspiration, the plastic tubes are tapped to remove any dry powder and the paper filter pushed with a wire plunger into the flask. Digestion of the flask contents is carried out on an electrically heated Kjeldahl rack with water-pump suction to remove any escaping fumes. The heaters are adjusted to give gentle refluxing so that digestion is complete in about 20 rain. After digestion, the sides of the flask are rinsed with 5 ml of distilled water, 1 ml of 2.5% ammonium molybdate solution is added, the flask swirled for mixing, 1 ml of 10% ascorbic acid solution is added, and finally 2 nfl of distilled water are added. The solution is transferred to a centrifuge tube~ heated in a boiling water bath for 5 rain, cooled, and suspended adsorbent removed by eentrifugation for 5-10 rain. Samples and blanks are transferred to euvettes and the optical density determined at 820 m/x af ter zero adjustment with water. Sensitivity can be increased by using a 10 nfl digestion flask and one half of the specified amounts of reagents. Glassware should be acid eleaned. Corrected optical densities are determined by subtraction of the reading obtained from a blank area corresponding in size to that of the sample. The values are then converted to tLg of phosphorus using a factor derived from a standard curve prepared using Na~HPO~. The factor in our laboratories is 11.0 for standard amounts and twice that for half amounts of reagents. Molar ratios of phospholipids are obtained by expression of results as percent of the total phosphorus in the sample. Deterruination of the total phosphorus is conveniently accomplished by spotting 50-100 t~g of total sample in a blank area (upper right corner) after development with both solvents. The total sample is then charred, etc., in the same manner as the samples. For expression of results as percent of the total lipid, phosphorus values for brain lipids are multiplied by the following' factors: phosphatidyl bmsitol, 31.4; phosphatidyl serine, 26.2; lecithin and phosphatidyl ethanolamine, 25.4 ; phosphatidic acid, 25.0; sphingomyelin, 24.8; and cardiolipin, 24.4 Aninml tissue lipid extracts are spotted at levels of 200-1000 ~g for determinations and at least four ehromatograms are developed with each of the two-dimensional systems. Average values for the major lipid classes (lecithin, sphingomyelin, phosphatidyl ethanolamine and phosphatidyl serine) are thus obtained from eight determinations. Usually spots from two eh roma tog ra ms are pooled for minor components. The values obtained from a normal adult human brain by the present procedure and the

Laboratory contaminants in lipid chemistry: Detection by thin-layer chromatography and infrared spectrophotometry and some procedures minimizing their occurrence.

Abstract: Many sources of contamination for lipid preparations exist in the laboratory. These contaminants can be detected using thin-layer chromatography (TLC) and infrared spectroscopy. Numerous components that are potential contaminants and can lead to false analyses were demonstrated by TLC in laboratory soaps, cleaners, hand creams and lotions, hair tonics, laboratory greases, floor waxes, oil vapors, tobacco smoke, hydrocarbon phases for gas-liquid chromatography, etc. Procedures preventing introduction of contaminants are presented including descriptions of equipment and precautions to eliminate or minimize contamination. These are useful in isolation of pure polar and nonpolar lipids.

A comparative study of the phospholipids and fatty acids of some insects

Abstract: Phospholipids of 27 species of insects representing 6 orders and 20 families were examined by DEAE cellulose column chromatography to determine the choline/ethanolamine phosphoglyceride ratios, and by gas chromatography to determine the constituent fatty acids.

A comparison of acyltransferase activities in vitro with the distribution of fatty acids in lecithins and triglycerides in vivo

Abstract: The location and configuration of a double bond in a fatty acid influences the rate of its acyltransferase-catalyzed esterification to form lecithin and its distribution in vivo between the primary and secondary positions of triglycerides and lecithins.

A micromethod for the stereospecific determination of triglyceride structure

Abstract: Triglyceride lipase and diglyceride kinase can be used in a sensitive stereospecific analysis of the separate fatty acid compositions at the 1, 2 and 3 positions of a triglyceride.Diglyceride kinase fromEscherichia coli selectively catalyzes the phosphorylation of 1,2-diglycerides but not the 2,3-diglycerides.The composition of the 3-position in rat liver triglycerides is clearly different from that at the 1-position.

Lipid peroxidation in rat tissue homogenates: Interaction of iron and ascorbic acid as the normal catalytic mechanism.

Abstract: Iron and ascorbic acid appear to be the normal catalytic components responsible for the lipid peroxidation reaction in aerobically incubated rat tissue homogenates. The amounts of each present in the catalytically-active fractions of rat liver, brain, testis, and kidney are appropriate to explain the lipid peroxidation reaction measured. Utilization of ascorbic acid as part of the normal catalytic mechanism is indicated by the following: The catalytic activity of the tissue soluble phase occurs only in the small molecule fraction eluted from Sephadex, and ascorbic acid occurs only in this fraction; the extent of catalysis by the small molecule fractions of the soluble phases from several tissues is proportional to their ascorbic acid content; and pH effect on lipid peroxidation is the same for both soluble-phase and ascorbic acid catalysis. Utilization of iron as part of the normal catalytic mechanism is indicated by EDTA inhibition studies and by measurements of pH effects. Previous studies have demonstrated the lack of catalytic activity by cations other than iron for the lipid peroxidation reaction in homogenates. Lipid peroxidation is inhibited at high tissue concentration and the inhibition is due to components occurring in the large molecule fraction of the soluble phase.

Determination of the specific positions ofcis andtrans double bonds in polyenes.

Abstract: A method is described for the determination of the positions and geometric configurations of double bonds in polyunsaturated fatty acids. The procedure consists of three steps: 1) Partial reduction of the double bonds with hydrazine under conditions which give high yields of monoenes. 2) Isolation of thecis- and thetrans-monoene fractions by thin-layer chromatography (TLC) directly or in the form of their ozonide derivatives. In the former technique, selective argentation is employed, in the latter, silicic acid adsorption. 3) Determination of the structure of the monoenes via reductive ozonolysis. The position of the double bonds is determined from the structures of the monoenes. Since thecis-monoenes are separated from thetrans-monoenes the geometric configuration of each double bond is determined.The method also provides a direct determination of the spacings of the internal double bonds and it may be employed for the determination of the structures of mixtures of fatty acids in conjunction with direct ozonolysis procedures. The various ramifications of the method are demonstrated on pure fatty acids and model mixtures thereof.

Metabolism of brain glycolipid fatty acids.

Abstract: The metabolism of the fatty acid moieties of brain cerebrosides, sulfatides, and gangliosides is reviewed and discussed. The methodology involved in the isolation of the fatty acids is described briefly. It seems clear now that most of these acids are made by chain elongation of intermediate length fatty acids by addition of acetate residues. The unsaturated acids are made by desaturation of the intermediate length acids (palmitic, heptadecanoic, stearic) followed by chain elongation. The hydroxy acids are made directly from the corresponding nonhydroxy acids, saturated, unsaturated, and odd-numbered. All the hydroxy acids undergo oxidative decarboxylation to yield fatty acids containing one less carbon atom. The odd-numbered acids are also made from propionate, which is elongated to intermediate length acids and then to longer acids. The major intermediate length “primer” acid seems to be palmitate, but there is evidence that the stearate used for cerebroside synthesis is also madede novo from acetate. The ganglioside fatty acids were found to turn over somewhat faster than the other fatty acids. Two metabolic pools for the cerebroside acids were found, one with a very high turnover rate, the other with a very low turnover rate.

Mass spectrometry of lipids. I. Cyclopropane fatty acid esters.

Abstract: A method was developed for the almost quantitative conversion of unsaturated esters (from monoenes to tetraenes) to cyclopropanes using diiodomethane and a highly active zinc-copper couple. These derivatives are sufficiently volatile for GLC analysis andcis andtrans isomers can be distinguished by this technique. Equivalent chain lengths of the cyclopropane derivatives were measured on polar and nonpolar phases. The mass spectra of the monocyclopropane compounds are very similar to those of the parent unsaturated esters. Those of dicyclopropanes, however, are quite distinctive so that the original structure of the ester can be deduced. Polycyclopropanes give complex spectra which are difficult to interpret in terms of the position of the original double bonds.

Influence of temperature on the fatty acid pattern of mosquitofish (Gambusia affinis) and guppies (Lebistes reticulatus).

Abstract: Adult male mosquitofish were adapted to 14–15C and 26–27C water temperature over a 14-day period and the fatty acids from their total lipids analyzed by gasliquid chromatography.

Reactions of dimethyl sulfoxide with sulfonate esters of fatty alcohols. I. Synthesis of higher saturated and unsaturated fatty aldehydes.

Abstract: Long-chain saturated fatty aldehydes (C10 to C18), as well as the C18 unsaturated aldehydes (oleyl, linoleyl, and linolenyl), were synthesized in good yields by the selective oxidation of the sulfonate esters of the corresponding alcohols with dimethyl sulfoxide in the presence of sodium bicarbonate. Chromatographic procedures for the isolation of the pure aldehydes from the reaction mixtures are described. The purity of the aldehydes was ascertained by thin-layer chromatography, melting points of their 2,4-dinitrophenyl hydrazones, infrared spectra and other physical methods.

Gas-liquid chromatographic analysis of long chain isomeric glyceryl monoethers.

Abstract: A quantitative method is described for the gas chromatographic analysis of glyceryl ethers using their trifluoroacetate (TFA) and trimethylsilyl (TMS) ether derivatives. Both derivatives are prepared at room temperature by reactions that proceed virtually to completion in less than 15 min, eliminating time-consuming derivative preparations and laborious clean-up steps of unreacted materials required by other methods. Gas-liquid chromatography (GLC) resolves the 1- and 2-isomers of the glyceryl ether TFA derivatives, which have not been separated previously. Purified synthetic 1- and 2-glyceryl ethers, including saturated and mono- and diunsaturated, were used to evaluate several polar and nonpolar liquid phases for the analysis of the TFA and TMS derivatives. Analyses can be made on some liquid phases normally used for methyl esters, while others are unsatisfactory. A mixture of isomeric C18 saturated and monoand di-unsaturated TFA derivatives was partially resolved; however, a complete analysis of this mixture can be made by preliminary separation of the unsaturates on silver-ion-impregnated thin-layer plates or by GLC analysis alone with three different phases.

The structure of the glycerides of ergot oils.

Abstract: The oils from sclerotia or from suitable mycelial cultures ofClaviceps purpurea (ergot) contain up to 44% of ricinoleic acid but no free hydroxyl groups. This is due to the presence of, besides normal triglycerides, tetra-acid, penta-acid and hexa-acid triglycerides. These contain respectively one, two and three ricinoleic acids esterified to glycerol, these in turn being acylated at their hydroxy groups with normal long-chain fatty acids. By suitable complementary use of TLC, GLC and lipase hydrolysis techniques, the proportions, compositions and structures of these novel triglyceride classes were determined. Four types of positional specificities in fatty acid combinations could be shown by our procedures. These are discussed and, on the basis of our results, some tentative proposals as to possible biosynthetic mechanisms are advanced.

Phospholipase a properties of several snake venom preparations.

Abstract: The hydrolytic properties of the venoms of seven species of snakes,Crotalus adamanteus, Ancistrodon contortrix, Naja naja, Bothrops atrox, Ophiophagus hannah, Crotalus atrox andVipera russeli, were studied with purified lecithins and mixtures of lecithins of known fatty acid and class composition as substrates.

Preparation of sulfate esters.

Abstract: This communication reports a new method for the synthesis of sulfate esters, in good yield, under mild conditions. Sulfuric acid reacts with an alcohol and dicyclohexylcarbodiimide in a polar solvent to produce sulfate esters.

Quinones and quinols as inhibitors of lipid peroxidation

Abstract: The influence of biological quinonoid compounds upon oxidative polymerization of lipids has been compared with that of simple quinones and antioxidants. A new procedure for the accelerated production and measurement of oxidative polymerization was used for this comparison. The biological quinones were found to be relatively ineffective as retarders of oxidative polymerization. Heme-catalyzed lipid peroxidation, as measured by oxygen uptake, was inhibited by ubiquinone and ubiquinol, both having about one fourth of the antioxidant capacity ofa-tocopherol. The peroxidation of mitochondrial lipid in vitro was inhibited by the presence of exogenous ubiquinone indicating that this compound may contribute towards the protection of the organelle in vivo.

Isomeric monoethylenic fatty acids in herring oil

Abstract: Monoethylenic fatty acids from herring oil were concentrated by chromatography by chromatography on silver nitratesilicic acid columns. Examination of consecutive fractions by open tubular gas chromatography confirmed the preferential elution of longer chain length esters and of esters within one chain length with the double bond closer to the terminal methyl group. Isomeric monoethylenic fatty acids with double bonds in the positions closer to the carboxyl group than the approximate midpoint of the even-numbered fatty acid chains could not be adequately separated by gas chromatography and were determined by ozonolysis. The isomers observed are consistent with primary formation from saturated acids through the action of an enzyme specifically removing hydrogen atoms in positions Δ9 and Δ10 relative to the carboxyl group. Chain extension of particular monoethylenic isomers by two carbon atoms in the C20 and longer chain lengths is apparently influenced by the position of the double bond.

Phospholipids of human serum.

Abstract: Phospholipids extracted from normal human serum were fractionated into lecithin, lysolecithin, sphingomyelin, phosphatidyl ethanolamine, lysophosphatidyl ethanolamine, phosphatidyl serine, and phosphatidyl inositol. Identification of each was established by thin-layer chromatography and infrared spectrophotometry. The content of plasmalogen was determined in both lecithin and phosphatidyl ethanolamine fractions. The composition of fatty acids and fatty aldehydes in isolated phospholipids is presented. The degree of unsaturation as reflected in the average content of double bonds per molecule of the fatty acids in phospholipids was: lecithin 1.2, choline plasmalogen 2.1, lysolecithin 0.6, sphingomyelin 0.2, phosphatidyl ethanolamine 2.8, lysophosphatidyl ethanolamine 1.0, phosphatidyl serine 1.0, and phosphatidyl inositol 1.8. Both chlline and ethanolamine plasmalogen aldehydes were predominantly saturated. Molecular weight of each phospholipid was calculated from determined fatty acid and fatty aldehyde compositions; the phosphorus factor for each phospholipid was computed. On a weight percent basis, lecithin, sphingomyelin, and lysolecithin accounted for 95% of the total phospholipids. The ethanolamine-containing phospholipids accounted for 2.5%, and the remainder was divided among phosphatidyl inositol, choline plasmalogen and phosphatidyl serine.

Gas‐liquid chromatographic analysis of cyclopropene fatty acids

Abstract: A gas-liquid chromatographic method is described for the quantitative estimation of cyclopropene fatty acids as their methyl mercaptan derivatives. This method estimates individual cyclopropene acids as well as normal and cyclopropane acids. Nine seed oils were analyzed for their cyclopropene fatty acid content.

Thermal reactions of methyl linoleate. I. Heating conditions, isolation techniques, biological studies and chemical changes.

Abstract: Methyl linoleate, diluted with an equal weight of methyl laurate, was heated without exclusion of air at 200C for 200 hours. The reaction mixture was separated by means of molecular distillation, urea adduction, column chromatography, and gas chromatography. Cyclic and aromatic materials were detected in the nonurea adductable monomer fractions. The dimer was separated into polar and nonpolar fractions. Analytical data for the nonpolar dimer are consistent with a cyclic Diels-Alder product. Bioassays showed the nonadductable monomer, the polar dimer, and a fraction of intermediate boiling point to be toxic when administered to weanling male rats. Urea-adductable fractions, nonpolar dimer, and polymer were not toxic. The concentrations of the toxic components were so low that the heated linoleate, before fractionation but after removal of the laurate, was not toxic.

Mass spectrometry of lipids. II. Monoglycerides, their diacetyl derivatives and their trimethylsilyl ethers.

Abstract: The mass spectra of 1- and 2-monoglycerides, their diacetyl derivatives and their trimethylsilyl (TMS) ether derivatives were recorded at high (80 eV) and low (6–13 eV) voltages. The fatty acid components of these derivatives included the even-numbered saturated acids from capric to arachidic acid plus oleic, linoleic and linolenic acids. Differences between isomeric 1- and 2-monoglycerides were not sufficient to provide a basis for the analysis of these isomers. Mass spectra of the monoglycerides were very similar to the corresponding methyl esters. Mass spectra of the diacetyl derivatives were qualitatively similar to triglycerides of long-chain fatty acids, but parent ions were not observed. The spectra of diacetyl derivatives may be used for distinguishing 1- and 2-monoglycerides, but the spectra of the TMS ethers are better in this regard. The latter derivatives have fragmentation patterns distinct for the 1- and 2-monoglyceride isomers, particularly at low electron voltages.

An unidentified lipid prevalent in tumors

Abstract: An unidentified lipid was found in five different tumor sources. It was not found in liver, bone marrow or plasma from tumor-bearing animals, nor in the extracellular fluid supporting growth of Ehrlich ascites cells. The polarity of the unidentified component was similar to that of a glyceryl ether diester, and it was isolated in milligram amounts by preparative thinlayer chromatography. Neither methyl esters of fatty acids, vinyl ether diesters nor quinones were found in the structural makeup of this lipid. Thin-layer chromatography of the purified unidentified tumor lipid on Ag-impregnated silica layers revealed two main components of intermediary unsaturation. Saponification of the unidentified tumor lipid, when water washing was omitted, yielded two components that migrated at Rf's identical to those of free fatty acids and dihydroxy glyceryl monoethers. Neither acetate-1-14C nor palmitic-1-14C acid (single injections) was found to be incorporated into the unidentified lipid of a mature rat tumor.

Fatty acids in phospholipids isolated from human red cells

Abstract: Total lipids of packed erythrocytes from healthy men 22 to 25 years old were extracted with chloroform-methanol mixture. Phospholipid classes were separated from neutral lipids and pigments on a silicic acid column. Phosphatidyl inositol (PI) was freed of its contaminants phosphatidyl ethanolamine (PE) and phosphatidyl serine (PS) on an aluminum oxide column. Additional silicic acid columns with modified solvent systems were needed for complete separation of other overlapped phospholipid classes. The identification of phospholipids in each eluted fraction was accomplished by TLC, using the appropriate spray tests and reference compounds, and confirmed on each of the isolated phospholipids by IR spectrophotometry. The total content of phospholipids as determined by phosphorus analysis was found to be 2.63 mg/ml of packed cells. These phospholipids were found to have the following composition (in per cent of total phospholipid): PI, 2.3; PE, 13.4; ethanolamine plasmalogen (EP), 14.5; PS, 3.9; lecithin (L), 34.2; choline plasmalogen (CP), 1.4; sphingomyelin (Sph), 28.4 and lysolecithin (LL), 1.7. The fatty acid composition of each phospholipid was determined by GLC. The average number of double bonds per fatty acid in the isolated phospholipids was found to be as follows: PI, 1.5; PE, 1.9; EP, 3.6; PS, 2.1; L, 1.0; CP, 2.0; Sph, 0.2 and LL, 0.5. The positional distribution of fatty acids in both L and PE was ascertained by selective enzymatic hydrolysis with phospholipase A. Saturated fatty acids of L were esterified predominantly in the α′-position, whereas in PE only 63.9 mole per cent of the saturated fatty acids were found in this position.

The isolation and partial characterization of gangliosides and ceramide polyhexosides from the lens of the human eye.

Abstract: The first isolation of glycolipids from the lens of the human eye is described. Neutral (ceramide polyhexosides) and acidic (gangliosides) glycolipids were separated by column chromatography and further resolved by thin-layer chromatography. The components were methanolyzed, converted to trimethyl silyl ethers and the ratios of the components determined. Two types of monosialogangliosides were found. The most abundant ganglioside contained long chain base/fatty acid/glucose/galactose/neuraminic acid in the ratio 1/1/1/2/1. The ratio of components of the minor ganglioside fraction was 1/1/1/1/1. Dihydrosphingosine was the major base and the major fatty acids were palmitate and nervonate. The ceramide polyhexosides all had a glucose/galactose molor ratio of 1/1 and the mixture of ceramide polyhexosides had a dihydrosphingosine/sphingosine molar ratio of 7.85. The fatty acids ranged from C10 to C25 with both odd and even carbon chains and were saturated or monounsaturated with palmitate, oleate, and nervonate predominating.

Fatty acid relationship in an aquatic food chain.

Abstract: The relationships amongst the fatty acids of the lipids from members of a model aquatic food chain were examined. The basic pattern of the fatty acids in the members, algae-brine shrimp-hydra, originated in the phytoplankton. Fatty acids in the neutral lipids of adult brine shrimp,Artemia salina, closely resembled dietary, or algal, fatty acids, whereas the phospholipid acids differed considerably from those in the algae. Fatty acids from the total lipids ofHydra pseudoligactis fed brine shimp nauplii also resembled the dietary acids, but more C20 polyunsaturates and fewer C18 unsaturated acids were present in those raised at 10C than were found at 20C.

Stereochemistry of α-parinaric acid fromImpatiens edgeworthii seed oil

Abstract: α-Parinaric acid is a major constituent fatty acid (48%) fromImpatiens edgeworthii Hook F. seed oil. Partial hydrazine reduction of the tetraene gave products which permit defining the stereochemistry of α-parinaric acid. Its structure iscis-9,trans-11,trans-13,cis-15-octadecatetraenoic acid. The tetraene readily reacts with maleic anhydride to give the Diels-Alder product with notrans-unsaturation. The formation of this adduct is contrary to previous reports.

A simple, rapid micromethod for the determination of the structure of unsaturated fatty acids via ozonolysis

Abstract: A micromethod for the localization of double bonds in unsaturated fatty acids via ozonolysis employing pyrolytic cleavage of ozonides in the presence of a hydrogenation catalyst is described. Cleavage of the ozonides is carried out in a gasliquid chromatographie instrument in a small glass tube, containing the catalyst, inserted in the top of the column opposite the in input heaters at 225C. Ozonides of methyl esters of straight chain unsaturated fatty acids are cleaved through the action of the catalyst to aldehyde fragments which are swept simultaneously into the column for analysis.

The synthesis of14C‐ and3H‐labeled glycerol ethers

Abstract: The racemic14C-and3H-labeled alpha and beta derivatives of octadecyl glycerol ether (batyl alcohol) and of hexadecyl glycerol ether (chimyl alcohol) of high specific activity were synthesized by treating the appropriate alkyl halides with a large excess of the potassium salts of isopropylidene or benzylidene glycerol. By use of the trifluoroacetic anhydride esterification procedure, the labeled diesters of alpha and beta octadecyl and hexadecyl glycerol ethers were prepared. The labeled monoesters of beta octadecyl and of beta hexadecyl glycerol ethers were isolated from the reaction mixtures by silicic acid column chromatography.

Determination of the structure of lecithins.

Abstract: A method is described for the determination of the classes of lecithins in terms of unsaturated and saturated fatty acids based on a total fatty acid composition, the composition of the fatty acids in the beta-position, and the amount of disaturated class determined via mercuric acetate adduct formation. The accuracy of the method was determined on lecithins of known composition and the method was applied to lecithins isolated from milk serum and egg lipids, safflower and soybean oils.