Influence of alkali concentration and other factors on the conjugation of natural polyunsaturated acids as determined by ultraviolet absorption measurements

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.