Sequential injection system for the spectrophotometric determination of reducing sugars in wines

摘要

A sequential injection system for the spectrophotometric determination of reducing sugars in wines is described.The methodology is based on the formation of a coloured complex produced by the reaction of copper (I) with2,9-dimethyl-1,10-phenanthroline (neocuproine), after reduction of copper (II) to copper (I) by reducing sugars. In thepresent SI system, a dialysis unit was incorporated not only to allow the sample dilution, but also to minimise theinterference of some coloured compounds. In this way, direct sample introduction into the system was possible,without any previous treatment of the wine samples. The proposed method can be applied to the determination ofreducing sugars in two concentration ranges: from 2 to 25 g l 1 (table wines) and from 20 to 140 g l 1 (Port wines).To perform determinations in these two ranges, the manifold configuration remained the same; just a few operationalparameters were changed in the controlling software. A sampling-rate of 14–18 samples per hour was obtained withgood repeatability for ten consecutive injections of wine samples (relative standard deviations (RSD) B2.1%). Theresults obtained from 19 wine samples were comparable to those obtained by the reference method.