SILVER ION CHROMATOGRAPHY AND GAS-CHROMATOGRAPHY MASS-SPECTROMETRY INTHE STRUCTURAL-ANALYSIS OF CYCLIC DIENOIC ACIDS FORMED IN FRYING OILS

Sixteen cyclic dienoic fatty acids formed from linolenic acid in linse ed oil heated to 275 degrees C were characterised after fraction by si lver ion high-performance liquid chromatography and analysis by gas ch romatography-mass spectrometry of the picolinyl esters and dimethyloxa zoline derivatives, before and after hydrogenation and deuteration. Th e stereochemistry of the double bonds were elucidated by gas chromatog raphy-Fourier transform infrared spectroscopy, Rings of eight cyclopen tenyl fatty acids (51% of the total cyclic dienes) were formed from C1 0 to C14 (22%) and C11 to C15 (29%) of the original chain with the dou ble bonds (C12 and C15, and C9 and C12, respectively) remaining in the ir original positions. Rings of eight cyclohexenyl fatty acids (49%) w ere formed from C10 and C15 of the original chain with double bonds at either C8 and C12 (26%) or C12 and C16 (23%). All possible combinatio ns of configurational isomers of both the cyclopentenyl/cyclohexenyl r ing and the double bond in the straight chain were formed. For the cyc lopentenyl fatty acids there were similar amounts of Z and E double bo nd isomers and a predominance of trans ring isomers, For the cyclohexe nyl fatty acids there was a predominance of E double bond isomers and similar amounts of both ring isomers.