Fast automated determination of total tocopherol content in virgin olive oil using a single multicommuted luminescent flow method

Tocopherols are natural fluorophores of great importance for the characterization and authentication of virgin olive oil. Herein, a single automatic multicommuted flow method has been developed for the determination of total tocopherol content as well as the semi-quantitative estimation of α-tocopherol in extra virgin olive oil (EVOO) samples. Only appropriate dilution of samples with 2-propanol was necessary for their direct analysis by a multicommuted flow injection (MCFIA) manifold based on three solenoid valves with fluorescence detection. The peak height at λ em = 330 nm (emission) with λ exc at 296 nm was used as analytical signal. Linear response was observed within the range from 50 to 350 mg of tocopherols (expressed as α-tocopherol kg−1 olive oil), suitable to cover the usual range for tocopherols in (extra) virgin olive oil ((E)VOO)). The results were consistent with those obtained by reversed-phase HPLC reference method, whereas the analysis time was significantly reduced. The sample frequency of the proposed automatic method was close to 40 samples h−1, in contrast to typically 15–30 min required by HPLC. The method is fast, straightforward, cost-effective, and easy to implement in routine laboratories for screening purposes.
The authors acknowledge funding support from the Regional Government of Andalusia (Spain), Junta de Andalucía (Project AGR-6066 and Research Group FQM323). F.J.L.-O. acknowledges a PhD student scholarship from MINECO (Ref. BES-2013-064014). B.G.L. acknowledges MINECO for her Juan de la Cierva postdoctoral research contract (ref. JCI-2012-12972).