Halogenated fatty acids: II. Methods of determination in lipids : II. Methods of determination in lipids

Halogenated fatty acids are the major contributors to organohalogen compounds in lipids of marine mammals, fish, and bivalves. For the initial characterization of these recently noticed compounds, a determination of the halogen concentration has usually been combined with some lipid isolation and separation method.

This review covers separation by solid phase chromatography, gel permeation chromatography, and liquid-liquid extraction, followed by halogen determination. All studies performed according to this outline have indicated that the major organohalogen compounds are chlorinated fatty acids bound in different lipids.

For the detection and identification of individual, halogenated fatty acid methyl esters (FAMEs) liberated from the lipids, gas chromatography (GC) has been employed together with detection methods such as electron capture detection, electrolytic conductivity detection (ELCD), atomic emission spectrometry, and mass spectrometry.

For most environmental samples, chlorinated FAMEs must be enriched prior to GC. ELCD is a useful detection method for indicating halogenated FAMEs in the chromatograms, and tentative identification of the halogenated species can be obtained by calculation of retention indices. For closer identification of halogenated FAMEs, mass spectrometry (MS) is very useful, in particular when employing the chemical ionisation mode.

MS identification, however, is highly facilitated if halogenated species are first indicated by element-selective methods.