The reduction of Cu(II)/neocuproine complexes by some polyphenols: Total polyphenols determination in wine samples |
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Authors: | Gina Lee Maura Vincenza Rossi Nina Coichev Horacio Dorigan Moya |
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Affiliation: | 1. Universidade Presbiteriana Mackenzie, CEP 01302-907 São Paulo, SP, Brazil;2. Instituto de Química, Universidade de São Paulo, CP 26.077, CEP 05599-970 São Paulo, SP, Brazil;3. Faculdade de Medicina da Fundação do ABC, CEPES (Centro de Estudos, Pesquisa, Prevenção e Tratamento em Saúde), CEP 09060-650 Santo André, SP, Brazil |
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Abstract: | A new method is presented for spectrophotometric determination of total polyphenols content in wine. The procedure is a modified CUPRAC method based on the reduction of Cu(II), in hydroethanolic medium (pH 7.0) in the presence of neocuproine (2,9-dimethyl-1,10-phenanthroline), by polyphenols, yielding a Cu(I) complexes with maximum absorption peak at 450 nm. The absorbance values are linear (r = 0.998, n = 6) with tannic acid concentrations from 0.4 to 3.6 μmol L−1. The limit of detection obtained was 0.41 μmol L−1 and relative standard deviation 1.2% (1 μmol L−1; n = 8). Recoveries between 80% and 110% (mean value of 95%) were calculated for total polyphenols determination in 14 commercials and 2 synthetic wine samples (with and without sulphite). The proposed procedure is about 1.5 more sensitive than the official Folin–Ciocalteu method. The sensitivities of both methods were compared by the analytical responses of several polyphenols tested in each method. |
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Keywords: | Wine Polyphenols Copper Neocuproine |
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