The OLEUM Protocol for Determination of the Total Hydroxytyrosol and Tyrosol Content in Support of the EU Authorized Health Claim for “Olive Oil Polyphenols”

An in-house validated ultra-high performance liquid chromatography (UHPLC) protocol for the purpose of supporting the health claim on “olive oil polyphenols” (EC Regulation 432/2012) is described. The method is based on the quantification of the total hydroxytyrosol (Htyr) and tyrosol (Tyr) content in the polar fraction of olive oil prior to and after acidic hydrolysis of their bound forms. The chromatographic analysis requires ~about one-third of the time needed under high performance liquid chromatography (HPLC) conditions, and thus, the eluent consumption per sample is sixfold lower. In addition to being cost-effective, more samples can be analyzed on a daily basis, thus, reducing the environmental footprint. Two external curves (Htyr, Tyr), detection at 280 nm, and correction factors for molecular weight difference of the hydrolyzed bound forms are proposed. The method is selective, robust with satisfactory precision (%RSD values <11%), and provides for recoveries higher than 87.6% for the target analytes (Htyr, Tyr). Standard operational procedures can be easily adopted for routine quality control of olive oil. The in-house validated protocol presents certain pros that should be exploited by the interested parties.