A method using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) for the determination of the fatty acid composition of vegetable oils is described and illustrated with the analysis of palm kernel oil, palm oil, olive oil, canola oil, soybean oil, vernonia oil, and castor oil. Solutions of the saponified oils, mixed with the matrix, meso-tetrakis(pentafluorophenyl)porphyrin, provided reproducible MALDI-TOF spectra in which the ions were dominated by sodiated sodium carboxylates [RCOONa + Na]+. Thus, palm kernel oil was found to contain capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, and stearic acid. Palm oil had a fatty acid profile including palmitic, linoleic, oleic, and stearic. The relative percentages of the fatty acids in olive oil were palmitoleic (1.2 +/- 0.5), palmitic (10.9 +/- 0.8), linoleic (0.6 +/- 0.1), linoleic (16.5 +/- 0.8), and oleic (70.5 +/- 1.2). For soybean oil, the relative percentages were: palmitoleic (0.4 +/- 0.4), palmitic (6.0 +/- 1.3), linolenic (14.5 +/- 1.8), linoleic (50.1 +/- 4.0), oleic (26.1 +/- 1.2), and stearic (2.2 +/- 0.7). This method was also applied to the analysis of two commercial soap formulations. The first soap gave a fatty acid profile that included: lauric (19.4% +/- 0.8), myristic (9.6% +/- 0.5), palmitoleic (1.9% +/- 0.3), palmitic (16.3% +/- 0.9), linoleic (5.6% +/- 0.4), oleic (37.1% +/- 0.8), and stearic (10.1% +/- 0.7) and that of the second soap was: lauric (9.3% +/- 0.3), myristic (3.8% +/- 0.5), palmitoleic (3.1% +/- 0.8), palmitic (19.4% +/- 0.8), linoleic (4.9% +/- 0.7), oleic (49.5% +/- 1.1), and stearic (10.0% +/- 0.9). The MALDI-TOFMS method described in this communication is simpler and less time-consuming than the established transesterification method that is coupled with analysis by gas chromatography/mass spectrometry (GC/MS). The new method could be used routinely to determine the qualitative fatty acid composition of vegetable oils, and, when fully validated by comparison with standard analytical methodologies, should provide a relatively fast quantitative measurement of fatty acid mixtures and/or soap formulations that contain saturated and unsaturated hydrocarbon moieties.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used for the characterization of a partially transesterified poly(beta-hydroxyalkanoate), PHA, polymer produced by the bacterial strain Alcaligenes eutrophus using saponified vegetable oils as the sole carbon sources. The transesterification was carried out separately under acidic and basic conditions to obtain PHA oligomers weighing less than 10 kDa. The intact oligomers were detected in their cationized [M + Na](+) and [M + K](+) forms by MALDI-TOFMS. A composition analysis, using the MALDI-TOF spectra, indicate that the oligomers obtained via acid catalysis were terminated with a methyl 3-hydroxybutyrate end group, and those obtained by base catalysis had a methyl crotonate (olefinic) termination. In addition to HB (hydroxy butyrate), the oligomers were found to contain a small percentage of HV (hydroxy valerate). This was independently confirmed using gas chromatography/mass spectrometry (GC/MS). In comparison, the analysis of a commercial PHA polymer, transesterified under identical conditions, only showed the presence of HB, i.e. a pure PHB homopolymer. Copyright 1999 John Wiley & Sons, Ltd.

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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, ...