Determination of furan fatty acids in extra virgin olive oil

The presence of 4 different furan fatty acids (F-acids) was detected in 18 samples of transmethylated monovarietal extra virgin olive oil: methyl 10,1 3-epoxy-11,12-dimethyloctadeca-10,12-dienoate [diMeF(9,5)], methyl 12,15-ep oxy-13,14-dimethyleicosa-12,14-d [diMeF(11,5)] and both olefinic derivative s of diMeF(11,5) with one unsaturation on the side chains conjugated with t he furan ring. Transmethylated oils were analyzed by normal phase high-perf ormance liquid chromatography coupled on-line with capillary gas chromatogr aphy. After the gas chromatographic separation step, a more selective detec tion of F-acids was achieved by using a photoionization detector mounted in series with a flame ionization detector. The concentration off-acids range d between 50 ppb (detection limit of the method) and 2.1 ppm in the oil. Th e olefinic derivatives of diMeF(11,5) acids detected were not artifacts cre ated during the sample preparation or during the chromatographic analysis.