Analysis of free fatty acids and fatty acid phenacyl esters in vegetable oils and margarine by capillary electrochromatography

Capillary electrochromatography (CEC) has been utilized to analyze free fat ty acids (FFAs) and fatty acid phenacyl esters (FAPEs) originating from veg etable oils and margarine. The analyses were performed on capillaries 25 an d 40 cm long, 100 mu m ID, and packed with 3 mu m Hypersil ODS. Isocratic e lution was achieved with the mobile phase acetonitrile/50 mM 2-(N-morpholin o)ethane sulfonic acid (MES), pH 6, at a ratio of 9:1. For quantitative ana lysis, the formation of FARE derivatives is preferred. Moreover, the number of double bonds in the FAPEs can be elucidated by measuring the UV absorba nce ratio of 240:210 nm. For the determination of the oleate/elaidate ratio in margarines, the FFAs are analyzed because of overlap of elaidate/palmit ate in FAPE analysis. Data obtained with CEC and micro liquid chromatograph y (LC) were compared and CEC was found to be far superior in terms of effic iency and speed of analysis. Important selectivity differences were noted b etween micro LC on highly endcapped ODS and CEC an the silanol-rich Hypersi l ODS.