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Food Lipids: Chemistry, Nutrition, and Biotechnology

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Figure 9 GC-EIMS spectra for the �13 <strong>and</strong> �14 pair of trans 18:1 DMOX positional<br />

isomers; the ions due to allyllic cleavage are at the following positions: �13, 238, 293, <strong>and</strong><br />

306 nm; �14, 252, 306, <strong>and</strong> 320 nm. (From Ref. 110.)<br />

D. LC-MS<br />

HPLC is the method of choice for the determination of both neutral <strong>and</strong> polar glycerol<br />

lipids. HPLC coupled with mass spectrometry (LC-MS) provides separation as<br />

well as unequivocal detection of all lipid species [134]. Application of thermospray<br />

HPLC was reported for the analysis of long chain carboxylic acids <strong>and</strong> their methyl<br />

esters [134,135]. This technique was paired with reversed phase HPLC to identify<br />

st<strong>and</strong>ard triacylglycerols <strong>and</strong> glycerophospholipids.<br />

The use of the electrospray technique with mass spectrometry was recently<br />

reviewed [136]. A dramatic increase in the use of this technique to analyze a variety<br />

of lipids, including complex mixtures of triacylglycerols, is expected in the near<br />

future.<br />

Using reversed phase HPLC coupled with flame ionization detection or quadrupole<br />

mass spectrometry with an atmospheric pressure chemical ionization source,<br />

the triacylglycerol compositions of margarine base stock products were determined<br />

[137]. These were highly-saturated vegetable oils, r<strong>and</strong>omized vegetable oils, vegetable<br />

oil–hard stock blends, <strong>and</strong> interesterified vegetable oil–hard stock blends. Triacylglycerol<br />

percent composition results for r<strong>and</strong>omized <strong>and</strong> interesterified test samples<br />

of known composition exhibited less average error using the HPLC quadrupole<br />

method, after application of response factors, than the results by HPLC coupled with<br />

Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.

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