Direct GC-(EI)MS determination of fatty acid alkyl esters in olive oils.

A new analytical method for fatty acid alkyl esters (FAAEs) determination by GC-MS in virgin olive oils is proposed. No sample preparation is required and FAAEs are directly thermo-desorbed and cryo-focalised in the cooled injector of a GC-MS (EI) instrument. The analytical conditions were optimized by Design of Experiment (DoE) techniques (an exploratory Plackett-Burman design followed by a factorial design on three selected variables). After the improvement of method performances, several samples of extra virgin and low quality virgin olive oils were analyzed both by the new method and by the Official EU Method of analysis. The application of Principal Component Analysis to the obtained results confirmed that the ability of the proposed method to discriminate between extra virgin and lower quality olive oils is at least equal to that of the Official Method, but the new method is faster, simpler, requires a much lower amount of organic solvents and significantly enhances method repeatability.