Fatty acid methyl esters, mass spectra

Figure 143. Distribution of fatty acid methyl esters (FAME), monoacylglycerols (MG), and diacylglycerols (DG) in a liquid injection field desorption ionization (LIFDI) mass spectrum of biodiesel (Schlichting et al., unpublished).

Figure 4.1 GC/MS analysis of methyl esters prepared from a whole cell lipid extract of the YEpOLEX-PDesat-TnD11Z-transformed ole1 strain of Saccharomyces cerevisiae (A) total ion spectrum of fatty acid methyl esters resolved by capillary GLC (B) mass spectrum of the degradation products of the DMDS adduct of Z11 -16 Me in A. The diagnostic m/z values of the DMDS adduct of Z11-16 Me are labeled. (Reproduced with permission from Knipple et al., 1998. 1998 by The National Academy of Sciences.)...

The 70 eV electron impact mass spectrum of laetisaric acid methyl ester gives a base peak at m/z 93 and a strong peak at m/z 292 due to a loss of water from the molecular ion at m/z 310. This indicates a molecular formula of C1gH3403. The 400 MHz NMR analysis of laetisaric acid methyl ester in deuterochloroform is characteristic of a fatty acid methyl ester of 34 protons with the presence of a nonconjugated dienol system 4.45 (1H,dt,J=8.4,6.3Hz), 5.31... 

Figure 12 The mass spectrum of the fatty acid methyl ester (FAME) of linolenic acid (C18 2A9-12) contains no readily discernable structural information beyond the molecular ion (a). However, the dimethyloxazoline (DMOX) derivative, in which the charge is retained by the heterocyclic ring, can undergo charge remote fragmentation yielding a mass spectrum from which the location of the double bonds, but not their geometry (c/ s versus trans), can be readily determined (b). The latter stereochemistry can usually be distinguished by the GC retention time on an appropriate column.

Kahlke and Richterich 1965) and plasma lipids of Refsum s (1946) case T. E. (Kahlke 1964 a). Methods and results were identical in both instances although a nuclear resonance spectrum was obtained only in the first case and a complete mass spectrometric analysis only in the second case. Phytanic acid was isolated by preparative gas-liquid chromatography from a mixture of fatty acid methyl esters. Traces of stearic acid were removed as the urea inclusion compound by treatment with a saturated methanolic solution of urea (Cason et al. 1953). After repeated crystallization from acetone at minus 70—80 C and drying under vacuum at minus 10 C, phytanic acid was obtained as a white crystalline powder with a melting point of minus 7—6 C. At room temperature phytanic acid is a colorless, odorless oil. The lack of hydrogen uptake with exhaustive... 

Py-MS is used to decrease sample preparation time for bacterial profiling. One method hydrolyzes and methylates fatty acids from bacteria without using chromatographic separation [87]. Figure 20.11 shows a pyrolysis-mass spectrum of fatty add methyl esters (fames) from four pathogenic bacteria. 

For example, the LIFDI mass spectrum of biodiesel from oilseed rape revealed methyl esters of long-chain fatty acids as typical plant lipid constituents (Figure 14.3). The most prominent signal originated from the methyl ester of oleic acid (Ci i, m/z 296.4), accounting to 42.6% of the TII, followed by the methyl esters of linoleic acid (Ciga,m/z 294.4,23.8%), linolenic acid (Cm-,m/z 292.4,4.4%), stearic acid (Ci8 o, m/z 298.5, 2.8%), palmitic acid (Ci6 0, m/z 270.4, 1.4%), and gondoic acid (C2o i,... 

Figure 6. Mass spectrum of perdeutero fatty acid (8 0) (as methyl ester) from run No. 5-44. The spectrum was taken as the compound was eluted from a glass column (1.8 m long X 0.4-cm i.d.) packed with 1% methyl silicone on diatomaceous earth and ionized by electron impact at 70 eV in a Hewlett-Packard 5730A gas chromatograph-mass spectrometer combination.

Products from Other Polyunsaturated Fatty Acids. Strain ALA2 converted EPA and DHA to THFA, (GC Rt of 24 and 37 min, respectively) (Fig. 5). The mass spectrum of the methyl ester/OTMSi ether of a product from EPA gave characteristic... 

The same hydrolytic conditions produced not only the fatty acid discussed in the previous paragraph, but also a more complex add. In the case of mycoside Q, the methyl ester had m.p. 53-55 °C, [a]o — 7° (chloroform). Its mass spectrum exhibited an intense peak at m/z 613 (C39H67NO4) (see Scheme 10) and peaks at m/z 162 (67) and 451 (66). This result showed that the fatty acid was linked by an amide bond to the D-phenylalanine residue in mycoside Q 180). A similar result was obtained for mycoside C1217 lb). 

The FT n.m.r. spectrum at 15.08 MHz of C-enriched methyl palmi-toleate (50), which was isolated from the lipid fraction, was recorded on 1.2 mg in CHCI3 solution. The spectrum showed enhanced signal intensities for the eight alternate carbon atoms (C-2, C-4, C-6, C-8, C-10, C-12, C-14, and C-16). This is the expected labelling pattern for the fatty acid derived from CH3C02Na. Mass spectrometry of the C-enriched ester indicated a 32% enrichment for the eight alternate sites. 

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