An Online-coupled HPLC-GC-FID Method for the Determination of Fatty Acid Methyl and Ethyl Esters in Olive Oil
Küchler, T.[1], Nestola, M.[2], Boysen, H.[1], Tablack, P.[2]
[1] Eurofins Analytik GmbH, Hamburg, Germany 
[2] Axel Semrau GmbH & Co. KG, Sprockhövel, Germany

Esters of fatty acids and short-chain alcohols in olive oil have been known for over 25 years. During the last few years, they came more into the focus of the general discussion as markers for the quality of virgin olive oils [1, 2]. Since April 2011, the Commission Regulation (EU) No 61/2011 has applied with limits for these parameters and an official method of determination. The aim is to detect fraudulent mixtures of extra virgin olive oils with lower quality oils whether they are virgin, lampante or some deodorised oils. With Regulation (EU) No 1348/2013, the limits were even tightened.

To avoid the manual sample preparation which contains high effort for the laboratory staff, an online-coupled HPLC-GC-FID system was used according to the studies of Biedermann et al. in the year 2008 [3]. We established an accurate and precise method for the determination of fatty acid methyl esters (FAME) and fatty acid ethyl esters (FAEE) which delivers results in one hour. The manual sample preparation effort was cut down by 90 % and reduced to the minimum. The working range of the method was 5 to 1000 mg/kg for every single methyl/ethyl ester, so current and future limits can be monitored easily. 

A welcome side-effect was that the HPLC-GC-FID equipment also can be used for a similar method for the determination of total sterol content resp. the sterol distribution as well as the waxes C42 to C46, which are also important parameters for the judgment of the quality of EVOO.

References
[1] Mariani & Fedeli (1986) Riv. Ital. Sostanze Grasse 63, 3-17.
[2] Pérez-Camino et al. (2008) J. Agric. Food Chem. 56(15), 6740-6744.
[3] Biedermann et al. (2008) Eur. Food Res. Technol. 228(1), 65-74.