Quantitation of hydroxytyrosol in food products using a sequential injection analysis fluorescence optosensor

• Method for automatic fluorimetric determination of hydroxytyrosol was developed.
• Use of solid support increases selectivity and sensitivity.
• Applied to the analysis of enriched foods.
• No matrix effect observed.

Hydroxytyrosol (HXT), one of the most important phenols in olive oil, has been reported to present beneficial effects for human health, such as antioxidant and antimicrobial properties and beneficial effects on the cardio-vascular system. As a result, exhaustive research is being carried out in order to use this compound in enriched foods, such as tomato juice or milk. In this paper, we propose a sequential injection analysis (SIA) optosensor for the fluorimetric (λexc/λem = 281/318 nm) determination of hydroxytyrosol in several foods. The use of a solid support in the flow-cell increases the sensitivity of the system (detection limit of 0.6 μg mL−1) and, especially, the selectivity. In this way, using a QuEChERS extraction procedure, the proposed method was applied to the determination of the analyte in hydroxytyrosol-enriched foods (tomato juice/soup, milk and infant formula). The recoveries (100 ± 10%) and relative standard deviations obtained (3–5%) show the potentiality of the developed system as an alternative to chromatographic methods.