Glass capillary gas chromatography‐mass spectrometry of wax esters, steryl esters and triacylglycerols

Abstract

Complex mixtures of wax esters, steryl esters and triacylglycerols isolated from representative biological and geochemical samples have been analyzed using combined high resolution gas chromatography and electron impact and chemical ionization quadrupole mass spectrometry. These low volatility neutral lipids containing up to 65 carbons were chromatographed intact on 15–20 m high‐temperature (upper limit: 370 C) persilylated SE‐52 and SE‐30 glass capillary columns. Discrimination effects due to adsorptive losses and degradation were minimized using a nonvaporizing on‐column injector and a direct all‐glass capillary connection (370 C) to the quadrupole mass spectrometer. Structural information regarding the fatty acid and alcohol moieties was found to be maximal for methane‐CI spectra in the case of wax and steryl esters, whereas EI spectra were most useful in interpreting triacylglycerol structures. Principal features of the EI and CI fragmentation patterns are discussed. The molecular composition of complex mixtures of these lipids is reconstructed for selected samples.

Long-chain wax esterns and diphenylamine in fire coral <i>Millepora dichotoma</i> and <i>Millepora platyphylla</i> from Saudi Red Sea Coast

“…The structural identification was confirmed by nuclear magnetic resonance analyses. It would be very interesting to compare and contrast the results of our studies with those of other groups workers (Aasen, 1971;Wakeham and Frew, 1982). The latter group have isolated all these four wax esters, but from particulate matter, and have stated that each one of these existed in three isomeric forms.…”

“…Identification of the compounds was based on comparison of retention indices and mass spectra of the analytes with literature data (e.g. Hites, 1992;Aasen et al, 1971;Wakeham and Frew, 1982) …”

“…Sargent found that this type of lipid is abundant in organisms that experience short periods of food plenty followed by long periods of food shortage. Wakeham and Frew (1982) have also reported the presence of wax esters from marine particulate matter. They found a mixture of saturated and unsaturated wax esters over the range C 28 -C 42 .…”

“…Identification of wax ester structures using different mass spectrometry methods was established (e.g. Aasen et al, 1971;Wakeham and Frew, 1982). These studies concluded that each peak is composed of a number of wax esters differing in alkyl and acyl moieties but having the same total carbon number (Wakeham and Frew, 1982).…”

“…Aasen et al, 1971;Wakeham and Frew, 1982). These studies concluded that each peak is composed of a number of wax esters differing in alkyl and acyl moieties but having the same total carbon number (Wakeham and Frew, 1982). This study aimed to investigate the chemical constituents of the two species of Millepora from the Saudi Red Sea, firstly by extracting the constituents by normal solvent extraction and secondly by subjecting the coral to mild acid hydrolysis.…”