ANALYSIS OF HYDROXY-CONTAINING SEED OILS USING ATMOSPHERIC PRESSURE CHEMICAL IONIZATION MASS SPECTROMETRY

Authors: Byrdwell, William; NEFF, WILLIAM

Submitted to: Journal of Liquid Chromatography
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: We have developed a new method of analysis which will be of particular importance/interest to scientists studying similar oils as described below. Previous methods were inadequate because fatty molecules in the oils broke apart, thus analysis could not be completed. This analysis will allow scientists to identify special properties (such as increased thickness or viscosity). The special properties of a fatty chain, ricinoleic acid, which comes from castor oil, has caused the U.S. Department of Defense to list this compound as an important and strategic material. Plants of the Lesquerella family also have special properties on their fatty chains, so they are being explored as possible replacements or supplements to the castor crop. This has allowed us to identify virtually all of the components in castor oil and two species of lesquerella--Lesquerella fendleri and Lesquerella gordonii.

Technical Abstract: Atmospheric pressure chemical ionization mass spectrometry (APCI-MS) coupled to reversed-phase high performance liquid chromatography (RP-HPLC) sed for direct analysis of intact triacylglycerols (TAGs) from hydroxy-containing plant oils. Castor bean oil, Lesquerella fendleri and Lesquerella gordonii, were separated into tri-hydroxy, di-hydroxy, mono-hydroxy and non-hydroxy TAGs using the RP-HPLC method. The APCI-MS ionization source produced fragments representing loss of zero (protonated molecular ion), one, two, and three hydroxy groups. The primary fragments (base peaks) in the mass spectra resulted from loss of all hydroxy groups from the TAGs. Using the acetonitrile/ methylene chloride solvent system, diagnostically important acetonitrile adducts were formed which allowed identification of the molecular weights of the hydroxy TAGs, as well as confirmation of the number of hydroxy groups contained therein. A series of four adducts was formed: [M+23]**+, [M+39]**+, [M+54]**+, and [M+59]**+. A mass difference of 76, 58, or 40 amu between the base peak and the [M+23]+ peak allowed the TAGs to be identified as tri-hydroxy, di-hydroxy, or mono-hydroxy, respectively. Additional fragmentation of the TAG occurred with cleavage of the acyl chains next to the hydroxy group giving a net loss of 114 amu. This fragmentation occurred in combination with loss of hydroxy groups from the remaining acyl chains. Diacylglycerol fragments were formed which also exhibited sequential loss of the hydroxy groups, as well as the fragment produced by loss of 114 amu.