mitted to an HP 85B computer, which performed intermediate concentration calculations and displayed a real time running plot of the Be data vs. depth. This procedure was extremely useful, enabling rapid identification of samples with suspect values and allowing immediate reinjection of the extracts. Full listings of both the integrator and computer programs are available from the authors. CONCLUSIONThe method outlined above is part of a continuing program aimed at developing and adapting analytical techniques for trace element determinations in natural waters. The techniques are developed to allow geochemical cycles to be delineated for elements where atomic absorption lacks sensitivity. For elements where other methods are available, ECD-GC of volatile chelates provides considerable advantages both in terms of sensitivity, lowering sample volume requirements and the associated collection problems, and suitability for use at sea. Currently the range of elements that have been determined at sea with this approach is Se (10) by 4-nitro-ophenylenediamine and Be, Al, and Cr by Htfa. The last two will be reported later. ACKNOWLEDGMENTWe wish to thank the Chief Scientist, Dean Roemmich, and the entire complement of the R.V. Thomas G. Thompson for both the opportunity to participate in, and their help throughout, the trans-Pacific cruise. Ed Boyle provided helpful comments on the paper as well as many useful sug-58, 2060-2072 2089 0 ID88 American Chemical Society

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.

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