Simultaneous determination of ethanol and glycerol in wines by a flow injection-pervaporation approach with in parallel photometric and fluorimetric detection.

A simultaneous method for the determination of ethanol and glycerol in wines based on the coupling of pervaporation-chemical derivatisation-photometric detection for ethanol and biochemical derivatisation-fluorimetric detection for glycerol is proposed. After separation by pervaporation the ethanol is collected in a K(2)Cr(2)O(7) acceptor stream and the Cr(3+) formed is driven to the spectrophotometer and monitored at 600 nm. The determination of glycerol is based on its oxidation by oxidised beta-nicotinamide adenine dinucleotide (beta-NAD(+)) catalysed by glycerol dehydrogenase immobilised on controlled-pore glass, the reduced form of the coenzyme (NADH) being spectrofluorimetrically monitored (lambda(ex)=340 nm, lambda(em)=460 nm).

Analytical pervaporation: a key technique in the enological laboratory.

This paper reviews the use of analytical pervaporation (defined as the integration of 2 different analytical separation principles, evaporation and gas diffusion, in a single micromodule) coupled to flow-injection manifolds for the determination of analytes of interest in enology; the review discusses the advantages that these techniques can provide in wine analytical laboratories. Special attention is given to methods that enable the determination of either of 2 volatile analytes, or of one volatile analyte and one nonvolatile analyte by taking advantage of the versatility of the designed approaches. In a comparison of these methods with the official and/or standard methods, the results showed good agreement.

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 anthocyanins in wine based on the coupling of continuous liquid-solid extraction, evaporation, HPLC individual separation and photometric detection is proposed. The target analytes are removed from the wine in a continuous fashion using a C18 minicolumn and eluted with an aqueous solution (pH 2) with 16% acetonitrile. The eluted fraction is concentrated by solvent evaporation assisted by heat and dragging off the vapour using a flow of N2.

Simultaneous (or sequential) determination of the total polyphenol index (or I280) and density in wines by flow injection.

Flow injection methods for the determination of the total polyphenol index, the 'index 280' (I280) and dissolved solids in wines are proposed. The determination of the total polyphenol index is based on the Folin-Ciocalteu reaction in a basic medium and subsequent spectrophotometric detection at 750 nm. The direct measurement at 280 nm of the wine allows the determination of I280 with a simple manifold.