A New Kinetic Spectrophotometric Method for Total Polyphenols Determination in White Wines
This paper describes a new, simple and sensitive catalytic kinetic spectrophotometric method for the determination of total polyphenols in white wines. The method was based on the catalytic effect of Cu(II) on the oxidation of phenolic compounds by H2O2 in acid media. The reaction was followed spectrophotometrically by measuring the increase in absorbance of oxidation products at 420 nm. Under optimal experimental conditions, a differential variation of the tangent method was used to obtain a calibration curve over the range of 23.01–194.11 g mL–1 of phenols. The calculated detection limit (3.3S0/b) was 6.77 g mL–1 for ten replicate measurements of blank signal. The relative standard deviations for five replicate determinations on 70.0, and 170.0 gmL–1 of galic acid were 2.49 and 1.79 %, respectively. The proposed method was successfully applied for the determination of total polyphenols in white wine samples and the results were in excellent agreement with the Folin-Ciocalteau method.
KEYWORDS: Kinetic-spectrophotometric method, phenolics oxidation, white wine.
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