Research Article Determination of polyphenols in wines by liquid chromatography with UV spectrophotometric detection This paper describes a new chromatographic method for the determination of poly- phenolic compounds in wines. The method is based on the separation of analytes by reversed-phase mode in a C18 column (2.6 mm particle size) and UV absorption spec- troscopy. The elution gradient is generated from 0.1% formic acid aqueous solution and acetonitrile as an organic modifier. Experimental conditions including pH, percentage of organic modifier and elution gradient profile have been thoroughly optimized using experimental design. A multi-objective function has been defined as a criterion for obtaining a satisfactory compromise among number of compounds separated, resolution and analysis time. Multi-detection at 280, 310 and 370 nm has been utilized in order to work under the most appropriate wavelengths for each compound. Figures of merit including linearity ranges, precisions, detection limits and recoveries have been estab- lished under selected experimental conditions using synthetic standards and commercial red wines. The method has been applied to analyze red wines from various Spanish regions. Keywords: Experimental design / Liquid chromatography / Multicriteria decision making / Polyphenols / Red wines / UV absorption DOI 10.1002/jssc.201000816 1 Introduction Polyphenols comprise a large family of naturally occurring wine compounds with important role in organoleptic properties of color and taste [1, 2]. The main polyphenolic components have been classified into several classes, namely hydroxybenzoic and hydroxycinnamic acids, antho- cyanins, procyanidins, flavanols, flavonols, stilbenes and tannins. It has been pointed out in various recent publications that contents of anthocyanins, proanthocyani- dins, etc. have a strong influence on color attributes of wines [3, 4]. For instance, malvidin, petunidin and peonidin (di)glucosides were recognized as characteristic descriptors of pigmentation of a given Italian-controlled designation of origin [5]. In another example, the bitterness, astringency and overall flavor of a series of Croatian red wines were found to be dependent on polyphenolic profiles [6]. Polyphenol profiles seem to be also related to oenological characteristics such as producing areas, grape variety and winemaking practices. As a result, contents of polyphenols can be exploited as a source of analytical data to establish wine classifications [7–12]. Evaluations of wine quality and detections of fraudulent adulterations can be thus based on polyphenolic profiles [13, 14]. Apart from sensory attributes, the influence of polyphenol composition on the antioxidant activity of wines deserves the attention of researchers [15, 16]. Other beneficial effects on human health partly attributable to polyphenols include anti-inflammatory, anti- microbial and cardioprotective activities [15]. Owing to the great relevance of polyphenols, analytical methods for their rapid, feasible and accurate determination in wines are increasingly required [17]. Most of the methods reported in the literature are based on HPLC with UV absorption spectroscopy [18–23]. The separation is typically based on reversed-phase mode. Mobile phases contain small amounts of mineral or organic acids (e.g. phosphoric, formic or acetic acids) in order to protonate polyphenols to obtain neutral species able to be separated in C18 or C8 analytical columns. Apart from UV detection, fluorescence [24, 25] and mass spectrometry [26–28] techniques are sometimes utilized to increase the sensitivity and selectivity of the methods. The sample treatment is often limited to simple wine filtration prior to injection. However, in some cases, preconcentration and clean-up procedures have been implemented to facilitate the detection of trace species while minimizing matrix interferences. Comments illustrating some recent examples are given as follows. A simple HPLC method with UV absorption spectroscopy was developed for the determination of common polypenolic constituents in Italian wines [29, 30]. O ` scar Aznar 1 Antonio Checa 1 Ramon Oliver 2 Santiago Herna ´ ndez- Cassou 1 Javier Saurina 1 1 Department of Analytical Chemistry, University of Barcelona, Barcelona, Spain 2 University School of Technical Engineering of Barcelona, Polytechnic University of Catalonia, Barcelona, Spain Received November 19, 2010 Revised December 14, 2010 Accepted December 15, 2010 Correspondence: Dr. Javier Saurina, Department of Analytical Chemistry, University of Barcelona, Diagonal 647, 08028 Barce- lona, Spain E-mail: xavi.saurina@ub.edu Fax: 134-934021233 & 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jss-journal.com J. Sep. Sci. 2011, 34, 527–535 527