Procedures are described for rapid lipase hydrolysis of triglycerides, isolation of the hydrolytic products by TLC and their conversion to methyl esters and fatty acid analysis by GLC. The techniques are applicable to a few mg of triglycerides or fats. Examples of data obtained with purified triglycerides i~dieate that the specific action of pancreatic lipase for the 1,3 ester groups is nearly absolute and the technique may be used as a criterion of purity of di-and tri-aeid triglycerides. Ca. 83% of the palmitie but only 10-12% of stearic and Cls unsaturated acids of commercial lard occur in 2-position.

SummaryMethyl esters were prepared from cholesteryl esters, phospholipids, and glycerides in substantially quantitative yields by methanolysis with large excess of sodium or potassium methoxide in absolute methanol.A silicic acid chromatographic adsorption column technique was described, which was effective in separating methyl esters from unsaponifiables such as sterols, pigments, etc., and free acids.Conditions for complete methanolysis of glyceride fats and oils requiring only 5 min. of reflux time were described.Quantitative conversion of fatty acids to methyl esters was accomplished by direct esterification with absolute methanol containing 4% HCL or H2SO4 and by methylation with diazomethane.

Rearrangement of 1-4 double bonds of diand polyolefinic compounds to the conjugated position has been shown to occur during treatment with catalysts such as nickel2'3 or alkali4'6 at high temperatures, and during autoxidation.6'7 Evidence for this change has been based to a considerable extent on spectroscopic data. Relatively little is known

Summary Optimum conditions for production of maximum conjugation of methyl arachidonate were determined. These comprise heating the sample in 21% KOH glycol for 15 minutes at 180°C. The optimum conditions of isomerization have also been applied to methyl linoleate, methyl linolenate, methyl eicosapentaenoate, and docosapentaenoate prepared by physical methods. These conditions greatly increased the sensitivity of the spectrophotometric method for all the polyun‐saturated acids except linoleic, for which the sensitivity was unchanged. Analyses of a series of fats and oils isomerized under optimum conditions and also under standard conditions were in good agreement. Constants are given for use when pentaene acids are present as well as for acids of less unsaturation. Spectroscopic evidence strongly indicates than pentaene acids are present in lard.

Summary Spectrophotometric methods of analysis for the polyunsaturated constituents of oils and fats have been carefully restandardized for several conditions of alkali‐isomerization, using purified methyl esters of linoleic, linolenic, and arachidonic acids prepared by physical rather than by chemical means. A number of vegetable oil and animal fat samples were subjected to spectrophotometric analysis, and the results based on natural and on bromination‐debromination fatty acid standards were compared. The natural fatty acid standards lead to significantly higher accuracy and their use in the spectrophotometric analysis of natural fatty materials is strongly recommended. Results obtained under different conditions of isomerization were in satisfactory agreement. An isomerization time of 45 minutes is recommended rather than 25 or 30 minutes. The glycerol‐air technique is preferred for general use because of its simplicity and high precision. The ethylene‐glycol‐nitrogen technique is a close second choice because of the greater transparency of reagent blanks.