No abstract

A fast‐drying sample preparation method, using α‐cyano‐4‐hydroxycinnamic acid as a matrix in an acetonitrile/tetrahydrofuran solvent system, has been used to obtain the matrix‐assisted laser desorption/ionization (MALDI) time‐of‐flight (TOF) mass spectra of commercial canola, castor and olive oils. The resulting spectra showed sodiated triacylglycerol molecules [M + Na]+. The canola oil contained at least eight triacylglycerols which were identified as: triolein, linoleoyldioleoylglycerol (OOL), dilinoleoyloleoylglycerol (OLL), trilinolein (LLL), dilinoleoyllinolenoylglycerol (LLLi), dioleoylpalmitoylglycerol (POO), linoleoyloleoylpalmitoylglycerol (POL) and dilinoleoylpalmitoylglycerol (PLL). The three brands of olive oil, Filippo Berio, Extra Virgin Pompeian and Progresso, were shown to contain triolein (OOO), OOL, OLL, POO and POL. The castor oil MALDI‐TOF spectrum was uncomplicated, indicating the occurrence of triricinolein (RRR), diricinoleoylstearoylglycerol (RRS), diricinoleoyloleoylglycerol (RRO), diricinoleoyllinoleoylglycerol (RRL) and palmitoyldiricinoleoylglycerol (RRP). Copyright © 1999 John Wiley & Sons, Ltd.

Quantitative analyses of fatty acids from five triacylglycerol products, coconut oil, palm kernel oil, palm oil, lard and cocoa butter, were carried out using two analytical methods: matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and gas chromatography (GC), in an effort to validate the application of MALDI-TOFMS in quantitative fatty acid analysis. For the GC analysis, transmethylated products were used, whereas, for the MALDI-TOF analysis, saponified products were used. Under MALDI-TOF conditions, the acids were detected as sodiated sodium carboxylates [RCOONa + Na](+) consistent with the mode of ionization that was previously reported. Thus, the MALDI-TOF mass spectrum of saponified coconut oil showed the presence of sodiated sodium salts of caprylic acid (7.5 +/- 0.67, m/z 189), capric acid (6.9 +/- 0.83, m/z 217), lauric acid (47.8 +/- 0.67, m/z 245), myristic acid (20.4 +/- 0.51, m/z 273), palmitic acid (9.8 +/- 0.47, m/z 301), linoleic acid (0.9 +/- 0.07, m/z 325), oleic acid (4.8 +/- 0.42, m/z 327) and stearic acid (2.0 +/- 0.13, m/z 329). Saponified palm kernel oil had a fatty acid profile that included caprylic acid (3.5 +/- 0.59), capric acid (4.7 +/- 0.82), lauric acid (58.6 +/- 2.3), myristic acid (20.9 +/- 1.5), palmitic acid (7.2 +/- 1.1), oleic acid (3.8 +/- 0.62) and stearic acid (1.2 +/- 0.15). Saponified palm oil gave myristic acid (0.83 +/- 0.18), palmitic acid (55.8 +/- 1.7), linoleic acid (4.2 +/- 0.51), oleic acid (34.5 +/- 1.5), stearic acid (3.8 +/- 0.26) and arachidic acid (0.80 +/- 0.22). Saponified lard showed the presence of myristic acid (1.5 +/- 0.24), palmitic acid (28.9 +/- 1.3), linoleic acid (13.7 +/- 0.67), oleic acid (38.7 +/- 1.4), stearic acid (12.8 +/- 0.64) and arachidic acid (2.4 +/- 0.35). Finally, for saponified cocoa butter, the fatty acid distribution was: palmitic acid (32.3 +/- 1.0), linoleic acid (2.6 +/- 0.35), oleic acid (34.9 +/- 1.7) and stearic acid (30.3 +/- 1.6). Quantitative gas chromatographic analysis of the corresponding methyl esters from these triacylglycerol products yielded data that were mostly in agreement with the MALDI-TOFMS data. The MALDI-TOF experiment, however, proved to be superior to the GC experiment, particularly with regard to baseline resolution of unsaturated acids. Furthermore, the ability of MALDI-TOFMS to detect low concentrations of fatty acids rendered it more sensitive than the GC methodology.

A fast-drying sample preparation method, using a-cyano-4-hydroxycinnamic acid as a matrix in an acetonitrile/tetrahydrofuran solvent system, has been used to obtain the matrix-assisted laser desorption/ ionization (

Matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) has been used to identify eight triacylglycerols (TAG) in Vernonia galamensis oil (VO). The TAG include trivernolin, divernoloylstearoylglycerol, divernoloyloleoylglycerol, divernoloyllinoleoylgylcerol, divernoloylpalmitoylglycerol, vernoloyllinoleoylstearoylglycerol, vernoloyllinoleoyloleoylglycerol, and vernoloyldilinoleoylglycerol. Samples for the MALDI/TOF/MS analysis were prepared with alpha-cyano-4-hydroxycinnamic acid (matrix) in an acetonitrile/tetrahydrofuran solvent system. A mol ratio of matrix/VO (44:1) gave reproducible composite spectra, resulting in resolutions greater than 8,000 and signal-to-noise ratios of above 1000 for the most abundant molecular species. 1,3-Dioleoyl-2-stearoylglycerol and 1,2-dioleoyl-3-palmitoylglycerol were used as calibration standards.Seed oils often consist of complex mixtures of closely related triacylglycerols (TAG), thus requiring time-consuming and demanding processes for their analysis. Determination of the fatty acid composition of these oils generally involves transmethylation, followed by chromatographic and mass spectrometric analysis (1,2). TAG are generally analyzed by thinlayer chromatography (TLC) and/or high-pressure liquid chromatography (HPLC) (3,4).Matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF)/mass spectrometry (MS) is an emerging and powerful tool that enables the analysis of complex mixtures of biomolecules such as proteins, peptides, and carbohydrates (5,6). Even though there are increasing reports of the use of MALDI TOF MS in the analysis of a variety of molecules, including synthetic polymers and oligomers (7,8), there is a major drawback in that it requires the use of an ultraviolet-absorbing molecule as a crystalline matrix for the sample preparation. Furthermore, the choice of matrix and the mode of sample preparation could be analyte-dependent, thus necessitating the development of specific sample preparation protocols for different types of molecules. However, in spite of such impediments, MALDI TOF MS could provide a simple and efficient characterization of the molecular species that are found in vegetable oils, once the sample preparation methodologies are developed.Vernonia galamensis oil (VO) is a new industrial oil which has recently been investigated for its potential use in coatings, polymer formulations, cosmetic formulation, and oleochemicals (9,10). VO is unique in that it consists mostly of naturally epoxidized triacylglycerols in which the major acid is cis-12,13-epoxy-cis-9-octadecenoic (vernolic) acid (11). We recently published the desorption chemical ionization/ mass spectrometry (MS)/MS investigation of VO in which seven TAG were identified (12).Consequently, the present study is aimed at the development of a simple and time-saving sample preparation method for the characterization of vernonia oils using MALDI TOF MS. EXPERIMENTAL PROCEDURESThe matrix, α-cyano-4-hydroxycinnamic acid (CHCA), acetonitrile, ...