Simultaneous (or sequential) determination of the total polyphenol index (or I-280) and density in wines by flow injection

Flow injection methods for the determination of the total polyphenol index, the 'index 280' (I-280) and dissolved solids in wines are proposed. The de termination of the total polyphenol index is based on the Folin-Ciocalteu r eaction in a basic medium and subsequent spectrophotometric detection at 75 0 nm. The direct measurement at 280 nm of the wine allows the determination of I-280 with a simple manifold. The dissolved solids determination is bas ed on the displacement of a light beam when the refractive index of the med ium changes. This phenomenon, followed by a change in the absorbance in a p hotometric detector, usually takes place when an injected sample reaches th e flow cell, and it is magnified on passage of the light beam in the radial direction instead of the more common axial direction. The use of a capilla ry (4 cm x 1.1 mm id) as the flow cell allows monitoring of the injected pl ug. A simple manifold coupled with a diode array spectrophotometer allows t he determination of these parameters with a frequency of at least 90 h(-1). Depending of the method adopted for the determination of polyphenols, Foli n-Ciocalteu or I-280, either a manifold different from that used for determ ining dissolved solids or the same, respectively, is required. The methods have been successfully applied to different wines and were substantiated we ll with official methods.