Micro-scaled Quantitative Method to Analyze Olive Oil Polyphenols

This study aims to improve an analytical method to quantify phenolic substances in olive oil. In order to minimize time required and quantity of solvents, sample extract preparation performed for a previously developed high-performance liquid chromatography–diode array detector to quantify olive oil polyphenols has been ten times downscaled and then validated. The new method performs the extraction of phenolic substances from 0.5 g of oil and allows to quantify the phenolic acids vanillic acid, p-coumaric acid, and ferulic acid; the phenolic alcohols tyrosol and hydroxytyrosol; secoiridoid derivatives; the lignans pinoresinol and acetoxypinoresinol; and the flavonoids luteolin and apigenin. Recoveries obtained were 66–89% for phenolic alcohols, 64–90% for phenolic acids, 93–96% for oleuropein (used as a reference for secoiridoid derivatives), 71–95% for flavonoids, and 97–100% for lignans. The total quantity of organic solvents used in the sample preparation is decreased from 30 to 3 mL with an important abatement of waste, costs, and working time requested.