Browsing by Author "Geto, Alemnew"

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    Determination of Total Polyphenols in Ethiopian Red Wines by Reaction with 4-Aminoantipyrine and Photometric Flow Injection Analysis
    (Addis Ababa Universty, 2007-08) Geto, Alemnew; Wodajo, Negussie (PhD)
    A simple flow injection spectrophotometric method for the determination of total polyphenols in red wines is reported. The method is based on the oxidative coupling of polyphenols with 4-aminantipyrine in alkaline medium to yield a colored product with maximum absorption at 470 nm. After optimization by univariant approach, the linear range was established between 9.4 to 451.5 mgL-1. The proposed system was applied for the determination of total polyphenols in Ethiopian red wines using gallic acid as the standard and the results are given as gallic acid equivalent (GAE) in mgL-1 with RSD < 1%. The method enabled analysis of approximately 43 samples h-1. The selectivity of the method was evaluated using compounds that are normally present in wine such as sugars, tartaric acid, ascorbic acid, methanol, ethanol, ammonium sulfate, and potassium chloride and it was found to be fairly selective (relative error < 4.2%). The method was validated through recovery test and the result was in the acceptable region 90.5% - 107.3%.