Determination of resveratrol in wine by photochemically induced second-derivative fluorescence coupled with liquid-liquid extraction.
Basic studies on the photochemical behaviour of trans-resveratrol and its photoproduct are reported. Photometrically and fluorimetrically calculated acidity constants of the former were determined. The usefulness of the determination of resveratrol by photochemically induced fluorescence and second-derivative photochemically induced fluorescence was also examined. The very weakly fluorescent trans-resveratrol is converted into a highly fluorescent photoproduct by irradiating hydroethanolic solutions of trans-resveratrol containing 40% v/v of ethanol for 60 s with intense UV radiation. The photoproduct presents excitation and emission maxima centred at 260 nm, and 364 and 382 nm, respectively. Under these conditions, a linear relationship between fluorescence intensity and trans-resveratrol concentration was found between 6.6 and 66 ng mL-1. Optimum conditions for the extraction of trans-resveratrol from an aqueous phase at pH 5.0 with diethylether were a phase ratio (aqueous/organic) of 2, a shaking time of 60 s and a buffer concentration of 0.15 mol L-1. An extraction recovery of 100% was reached under these conditions. The optimized extraction procedure was applied to the analysis of resveratrol in wine samples, employing the amplitude between 356 and 364 nm of the second-derivative photoinduced emission spectrum as analytical signal. It was found that there is not matrix effect and recoveries around 100% were obtained at different fortification levels.
Galeano Díaz
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T
Department of Analytical Chemistry, University of Extremadura, 06071, Badajoz, Spain.
Durán Merás
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I
Airado Rodríguez
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D
D015394:Molecular Structure; D010777:Photochemistry; D000077185:Resveratrol; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013267:Stilbenes / Q000032:analysis* / Q000737:chemistry*; D014920:Wine / Q000032:analysis*
D013267:Stilbenes; D000077185:Resveratrol