Use of relationships between retention behaviors and chemical structures in subcritical fluid chromatography with CO2/modifier mixtures for the identification of triglycerides.
Satisfactory separations of vegetable oil triglycerides (TG) differing in fatty acid composition are obtained by subcritical fluid chromatography (SubFC) with octadecyl packed columns and CO2/modifier mobile phases. However, the identification of TG can be sometimes difficult due to the small retention differences between the compounds. A method of TG identification in SubFC was achieved, which does not require calculation of retention pattern but uses the differences in retention behavior related to TG structure and to the nature of the subcritical mobile phases. These retention differences were produced by the variation of either outlet pressure or modifier percentage or of temperature. Whatever the column aging, this method allows the determination of the triglyceride total chain length and double bond number. Among numerous structures, these two criteria restrict the structural hypothesis at worst to three or four possibilities and sometimes only to one. The validity of this relative identification method was confirmed by electronic impact mass spectrometry of triglyceride fractions collected from the analysis of a peanut oil. The analysis of concentrated fractions is favored by the spontaneous elimination after the pressure regulator of carbon dioxide, the main fluid of the subcritical mobile phase.
Lesellier
E
E
LETIAM, IUT ORSAY, France. lesellier@iut-orsay.fr
Bleton
J
J
Tchapla
A
A
D002245:Carbon Dioxide; D002853:Chromatography, Liquid; D013058:Mass Spectrometry; D010938:Plant Oils / Q000737:chemistry*; D014280:Triglycerides / Q000737:chemistry*
D010938:Plant Oils; D014280:Triglycerides; D002245:Carbon Dioxide