UTILIZATION OF HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY AS AN ENRICHMENT STEP FOR THE DETERMINATION OF CYCLIC FATTY-ACID MONOMERS IN HEATED FATS AND BIOLOGICAL SAMPLES

A method was developed to determine traces of cyclic fatty acid monome rs (CFAM) in oils and animal tissues. This method is a combination of some techniques developed earlier but with the enrichment step being a chieved by high-performance liquid chromatography (HPLC) instead of ur ea inclusion. After transformation of the lipids into methyl eaters, t he latter were hydrogenated after addition of an internal standard (me thyl heptadecanoate or ethyl hexadecanoate). The mixture was enriched in CFAM by HPLC on a semi-preparative C-18 reversed-phase column using acetonitrile-acetone (90:10, v/v) at 4 ml/min. The enriched fraction containing the CFAM and the internal standard was then analysed by gas chromatography on a polar column (cyanosilicone phase). This method w as developed using known mixtures of CFAM isolated from both heated su nflower and Iinseed oils. Small amounts of CFAM (50 mu g/g of sample) were determined with good reproducibility without any loss during the HPLC enrichment step and with no modification of the relative proporti ons of the CFAM in the mixture. This method can be applied to either h eated fats and oils or biological samples (heart cell culture) that co ntain only traces of CFAM. Ethyl hexadecanoate (16:0 ethyl ester) can be used as an internal standard for samples containing small amounts o f 17:0.