GAS–LIQUID CHROMATOGRAPHY OF TERPENES: PART III. THE USE OF OLEIC ACID ESTERS AS LIQUID PHASES

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Abstract
The separation of several cyclic terpene hydrocarbons and some oxygenated derivatives was studied on a variety of triglyceride and dioleate ester columns. Use of rapeseed oil, partially hydrogenated rapeseed oil, olive oil, triolein, tristearin, methyl oleate, and potassium oleate as liquid phases led to the conclusion that the presence of an esterified mono-unsaturated long-chain acid is a desirable constituent of the liquid phase. Dioleate esters of 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, and polyethylene glycol showed useful differences in the degree of separation of both terpene hydrocarbons and oxygenated derivatives. Ether linkages, as in the di- and poly-ethylene glycol ester, also were associated with favorable separations. When the liquid phase contained free hydroxyl groups, the degree of separation of hydrocarbons and ketones was in general less favorable. The spacing of the ester groups was found to have some effect on retention data. The separation of such critical pairs of isomers as tricyclene and α-pinene, α-fenchene and camphene, and also geometrical isomers of oxygenated derivatives is facilitated by use of several of these liquid phases.