Determination of major triacylglycerol components of polyunsaturated specialty oils using matrix-assisted laser desorption ionization time-of-fight mass spectrometry

Five specialty oils; flaxseed, walnut, sesame, grapeseed and hazelnut, have been analyzed by matrix-assisted laser desorption ionization (MALDI) time- of-flight (TOF) mass spectrometry (MS). alpha-Cyano-4-hydroxycinnamic acid, dissolved in acetonitrileite/trahydrofuran, was used as the matrix. The MA LDI-TOF mass spectra produced only sodiated triacylyglycerol molecules [M Na](+). The flaxseed oil contained ten major triacylglycerols (TAGs) which include triolein (OOO), linoleoyldioleoylglycerol (OOL), dilinoleoyloleoyl glycerot (OLL), trilinolein (LLL), linolenoyldilinoleoylglycerol (LLLn), di linolenoyllinoleoylglycerol (LLnLn), trilinolenin (LnLnLn), dilinoleoylpalm itoylglycerol (PLL), linolenoyllinoleoylpalmitoylglycerol (PLLn), and dilin olenoylpalmitoylglycerol (PLnLn). The walnut oil also contained ten major T AGs that were identified as: OOO, OOL, OLL, LLL, LLLn, LLnLn, POO, POL, PLL , and PLLn. Eight major TAGs were identified in the spectrum of sesame oil, including dioleoylstearoylglycerol (SOO), OOO, OOL, OLL, LLL, POO, POL, an d PLL, The grapeseed oil was found to contain seven major TAGs: OOO, OOL, O LL, LLL, POO, POL, and PLL. Six major TAGs were identified in the spectrum of hazelnut oil as OOO, OOL, OLL, LLL, POO, and POL. When palmitoyldistearo ylglycerol (PSS) was used as an internal mass calibrant with each of the sp ecialty oils, there was a suppression of the sodiated PSS signals, implying that TAGs containing unsaturated fatty acids may have greater affinities f or sodium ions than those that contain only saturated acid moieties. The im plication of such a trend is that a sample preparation method that does not significantly discriminate against saturated TAGs should be developed for quantitative studies involving mixtures of saturated and unsaturated TAGs. Copyright (C) 1999 John Wiley & Sons, Ltd.