Determination of anthocyanins in wine based on flow-injection, liquid-solid extraction, continuous evaporation and high-performance liquid chromatography-photometric detection

A continuous method, easy to automate, for the determination of anthocyanin s in wine based on the coupling of continuous liquid-solid extraction, evap oration, HPLC individual separation and photometric detection is proposed. The target analytes are removed from the wine in a continuous fashion using a C-18 minicolumn and eluted with an aqueous solution (pH 2) with 16% acet onitrile. The eluted fraction is concentrated by solvent evaporation assist ed by heat and dragging off the vapour using a flow of N-2. For in-line pre concentration, a continuous evaporation module was designed and located in the manifold between the solid-phase minicolumn and the injection valve of the chromatograph. In this way, injection of the sample into the dynamic sy stem leads the plug through it for liquid-solid extraction of the anthocyan ins, partial evaporation of the eluent (with a preconcentration factor as r equired) and transport to the high-pressure injection valve of the chromato graph, where individual separation and subsequent photometric detection tak e place. The method thus developed for the determination of malvidin-3-gluc oside, cyanidin-3-glucoside and peonidin-3-glucoside anthocyanins in Spanis h red wines is more sensitive than the batch manual method based on the sam e steps, has better linearity of the calibrations curves with lower detecti on limits and much wider determination range for the most abundant anthocya nins in wine. In addition, the method can be fully automated with low acqui sition and maintenance costs. (C) 2001 Elsevier Science B.V. All rights res erved.