HPLC analysis of underivatized fatty acids in margarines

The composition of the underivatized fatty acids in margarines was determined by high performance liquid chromatography (HPLC). A 50-min analysis gave not only the distribution of the cis- and trans-isomers of the 18 carbon-length, but also a quantitative measure of seven of the underivatized fatty acids studied. High concentrations of the essential fatty acid, linoleic acid, were found in the four margarine samples. Results of the quantitation, reproducability of the HPLC analysis, and stability of the standards are discussed. It was found that the developed HPLC analysis was able to adequately separate the geometric isomers, linoleic acid (18:2 delta 9c, 12c) from linolelaidic acid (18:2 delta 9t, 12t). However, a mixture of the other two isomers, 18:2 delta 9c, 12t and 18:2 delta 9c, 12c coeluted together between the peaks due to the 18:2 delta 9c, 12c and 18:2 delta 9t, 12t isomers. This study did not attempt to separate the various positional isomers of underivatized fatty acids.