Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2012
Publication Date: 1/1/2013
Citation: Lin, J.T., Chen, G.Q., Hou, C.T. 2013. Mass spectrometry of the lithium adducts of diacylglycerols containing hydroxy FA in castor oil and two normal FA. Journal of the American Oil Chemists' Society. 90:33-38.
Interpretive Summary: Castor oil has been used in industry such as the manufacture of biodegradable plastics, nylon, plasticizers, lubricants, cosmetics and paints. Castor oil contains mostly triacylglycerols containing hydroxy fatty acids. Twelve diacylglycerols containing hydroxy fatty acids in castor oil were identified by mass spectrometry. The spectra of these diacylglycerols were compared with those of the diacylglycerols containing two normal fatty acids.
Technical Abstract: Castor oil can be used in industry. The molecular species of triacylglycerols containing hydroxy fatty acids (FA) in castor oil have been identified. We report here the identification of twelve diacylglycerols (DAG) containing hydroxy FA in castor oil using positive ion electrospray ionization mass spectrometry of the lithium adducts. They were RR (diricinolein, R is ricinoleate), RL, RS, R-diOH18:0, R-diOH18:1, R-diOH18:2, R-triOH18:0, R-triOH18:1, R-triOH18:2, diOH18:0-diOH18:1, diOH18:1-diOH18:1 and diOH18:1-diOH18:2. The MS2 fragment ions, [M + Li - FA]+ and [FA + Li]+, from the lithium adducts of DAG containing hydroxy FA (one or two hydroxy FA), were used for the identification. The additional fragment ions from the neutral losses of FA lithium salts [M + Li - FALi]+ were used for the identification of eleven DAG containing two normal FA in a soybean oil bioconversion product. The MS2 fragment ions from the neutral losses of FA lithium salts [M + Li - FALi]+ were not detected from the DAG containing hydroxy FA. The DAG containing FA with more hydroxyl group than the other FA on the same DAG molecule tend to have prominent fragment ion, [FA + Li]+ and undetectable fragment ion [M + Li - FA]+ while the FA is the more hydroxylated FA. Also the less hydroxylated FA of a DAG tend to have prominent fragment ion, [M + Li - FA]+ and undetectable fragment ion [FA + Li]+ while the FA is the less hydroxylated FA.