How should we measure n-3 polyunsaturated fatty acids and their metabolites in humans?

Growing interest in nutritional intervention with n-3 polyunsaturated fatty acids demands reliable analyses of these fatty acids and their corresponding eicosanoids in vivo or ex vivo. n-3 polyunsaturated fatty acids are preferably assayed by capillary gas-liquid chromatography after extraction of the lipid classes, their separation by chromatographic methods and conversion of the fatty acids to methylesters. n-3 eicosanoids have to be separated from their arachidonic acid analogues by HPLC or by gas-liquid chromatography and are then quantified by UV-spectroscopy or mass-spectrometry. Structure elucidation has to be performed by chemical reactions and by mass spectrometry. Antibodies for radioimmunoassays against n-3 eicosanoids are not yet available.