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Standardization of spectrophotometric methods for determination of polyunsaturated fatty acids using pure natural acids
Author(s) -
Brice B. A.,
Swain M. L.,
Herb S. F.,
Nichols P. L.,
Riemenschneider R. W.
Publication year - 1952
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02631475
Subject(s) - isomerization , chemistry , polyunsaturated fatty acid , glycerol , ethylene glycol , organic chemistry , linoleic acid , reagent , chromatography , fatty acid , catalysis
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.