RESEARCH Key Ci β Unsaturated Fatty Acids Separated
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Atherosclerosis Breakthrough Gas chromatography advances lead to quick sepa ration of key fatty acids from complex lipids A
BIG BREAKTHROUGH toward unravel
ing the role of fatty acids in liquid me tabolism a n d atherosclerosis: Oleic, linoleic, and linolenic acids—biologically important C 1 8 unsaturated fatty a c i d s can now be separated quickly b y gas chromatography from complex lipid mixtures. These three fatty acids may be keys to questions on fat metabolism in humans and perhaps atherosclerosis. These new developments in high tem perature gas chromatography open the door to detailed study of "essential" fatty acids and fats in human diets, says S, R. Lipsky, Department of Internal Medicine of Yale Medical School. Researchers know that cholesterol is involved in atherosclerosis; fats in hu man diets, too, are part of t h e picture. Now, many scientists think that oleic, linoleic, and linolenic acids, along with arachidonic acid, may play key roles in how people use fats, and maybe in atherosclerosis. Rut until now, research on fats and atherosclerosis has been stymied by lack of proper analytical tools—existing methods were time consuming. Very little is known about diet content of oleic and its isomers and about how the body uses them. T o top off the prob lems, sample sizes in this work are usually around 1 mg.—a kingsized ana lytical headache. 48
C&EN
FEB. 3,
1958
• Industry Gets Ball Rolling. Indus try, too, was growing more aware of the problems of fats and metabolism. Working on t h e theory that two heads are better than one, t h e Institute of Shortening a n d Edible Oils took indus try's problems to t h e National Heart Institute, old hands at research in ather osclerosis. Result—the Committee on Problems of Lipid Analysis, with E. C Horning of t h e National Heart Institute as chairman, was formed last May. Biggest problem facing the commit tee was finding a fast, reliable method for analysis of fats a n d fatty acids through at least C22· Best path to fol low seemed to be high temperature gas chromatography, using techniques de veloped by A. James a n d A. Martin i n England. But the British hadn't sepa rated linoleic from linolenic acid. Meanwhile, in the United States, Lipsky h a d done much work toward developing his own gas chromato graphic equipment and techniques for fatty acids. While results soon equaled those of t h e British, h e saw a need for better resolution of the key C 1 8 group. Resolution time was also too great. The committee turned to instrument makers, food industry laboratories such as those of Procter and Gamble, Ar mour, and Swift, and to the chemical industry. Lipsky and his group worked
toward further development of an in strument t h a t met the exacting specifi cations needed. T h e result of t h e work at Yale—a custom-built gas chromatograph readily used for separating microquantities of long-chain fatty acids. Several such instruments a r e new being Built for u s e b y collaborat ing labs. • N e w Liquid Phases. But t h e critical C 1 8 unsaturated group remained elusive. Liquid phases used weren't giving s h a r p separations in the wanted range. N e w liquid phases were screened, a n d Procter a n d Gamble's J. E . Callen and C . H . Orr hit pay dirt with a polymer—Reoplex 400, a poly ester m a d e b y Geigy Chemical. At a b o u t the same time, Lipsky found two other partition agents that would separate unsaturated acids: LAC-l-R 2 9 6 , t h e adipate polyester of diethylene glycol, a n d LAC-2-R 446, adipate polyesters of diethylene glycol partially cross-linked with pentaerythritol, both made by Cambridge In dustries. Use of these n e w liquid phases in t h e n e w instruments led to good, quantitative separation of oleic, linoleic, a n d linolenic acids. A third piece of the puzzle, the sens ing element, has been put in place also. Much of t h e experimental work was done using thermal conductivity type detectors. Results showed that much greater sensitivity was desirable. Plans now call f o r tests with new sensing sys tems such a s beta ionization, with krypton-85 as a source, a n d gas type detec tors.
