Fractionation of Coconut Oil Triglycerides by Gas-Liquid Chromatography

A system is described for separation by gas-liquid chromatography and collection of milligram quantities of triglycerides having the same number of carbon atoms. The system includes a stainless steel column (3/16 in., o.d., × 6 ft) packed with 1% w/w JXR on 100/120 mesh Gas-Chrom Q, which gives satisfactory separation in each run of about 3 mg of a mixture of triglycerides; a stream-splitter at the column outlet for collection of each triglyceride peak; and a pre-column placed in the injection block to provide on-column injection. These units are installed in an F & M 1609 apparatus with flame ionization detector. Trilaurin-14C was used both to indicate that detection and collection of a triglyceride peak were simultaneous and to study peak trailing quantitatively. Peak trailing, which is largely responsible for contamination of peaks collected later, is always very slight—about 1% for the peak immediately following—and then decreases progressively. The described method was applied to separation and collection of triglyceride peaks from coconut oil, and the purity of collected peaks was monitored. The degree of purity is generally excellent except in the case of late-eluting peaks. There is significant contamination of these peaks, present in low concentration in the mixture, due to tailing of preceding peaks that are present in high concentration. It is therefore essential to rechromatograph the impure peaks at least once in order to carry out later as exact an analysis of each as possible.