Characterization of fatty acid isomers in dehydrated castor oil by gas chromatography and gas chromatography-mass spectrometry techniques

Fatty acid isomers present in dehydrated castor oil were analyzed by gas chromatography and gas chromatography‐mass spectrometry (GC‐MS) of their dimethyl oxazoline derivatives. Conjugated linoleic acid 9,11 and 10,12 isomers were identified by GC based on equivalent chainlengths. Segmental peak analysis of GC‐MS total ion chromatogram mass fragmentation pattern revealed the presence of 7,9 and 8,10 conjugated linoleic acids along with 9,11 and 10,12 conjugated linoleic acids. Interestingly, a reverse elution of trans, trans‐conjugated linoleic acids was observed, viz. 10,12 was followed by 9,11, which was in turn followed by the 8,10 and 7,9 isomers. The observed reverse order of elution was in contrast to the conventional elution pattern of both nonconjugated and conjugated cis,cis‐, cis,trans‐ and trans,cis‐isomers.