Author's personal copy Talanta 71 (2007) 1455–1463 Determination of phenolic acids in strawberry samples by means of fast liquid chromatography and multivariate curve resolution methods S´ ılvia Mas a , Gemma Fonrodona b , Rom` a Tauler a,∗ , Jose Barbosa b a Department of Enviromental Chemistry, IIQAB-CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain b Department of Analytical Chemistry, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Spain Received 10 January 2006; received in revised form 16 June 2006; accepted 6 July 2006 Available online 12 September 2006 Abstract Use of Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) is evaluated in the analysis of nine phenolic acids, both in standards mixture samples and in strawberry juice samples, by liquid chromatography with diode array detection (LC-DAD). Chromatographic coelution problems either because of unknown matrix interferences or because of the increase of organic modifier to reduce chromatographic analysis times are investigated. pH (4.25) and proportion of organic modifier in acetonitrile–water ratios (11:89, v/v) used as mobile phases have been optimized for separation of mixture of nine phenolic acids. Results obtained in the resolution and quantitation of phenolic acids in standards mixture samples and strawberry samples at two proportions of organic modifier (11:89 and 40:60 acetonitrile–water (v/v) ratios) show that the proposed MCR-ALS approach reduces analysis times and solvent expenses and improves determinations in case of strong coelution. Limits on the use of MCR-ALS are investigated in the analysis of phenolic acids in strawberry samples. © 2006 Elsevier B.V. All rights reserved. Keywords: Phenolic acids; MCR-ALS; LC-DAD; Coelution 1. Introduction During the last decades, the scientific community has recog- nized the value of vegetables and fruits, not only as a nutrient source, but also as a good for vitaminical deficiencies prevention. For many years, beneficial effects of some fruits and plants have been known. Their consume provides reduction of heart dis- eases, free radicals and hypertension, improvement on weight control and even reduction of the risk of some cancers (cervix, ovary, prostate, liver, kidney, etc.) [1]. Many of these beneficial effects are attributed to phenolic acids present in vegetables and fruits. These phenolic acids are bioactive compounds and they are widely distributed in the vegetal world. They take part in the diary diet and they influence the health. It has been demon- strated that they act as antioxidants, anti-inflammatories, anti- histaminics and anti-tumorals. Moreover, phenolic acids have been associated with color, sensory qualities and nutritional and conservation properties of aliments [2]. ∗ Corresponding author. Tel.: +34 93 400 61 40; fax: +34 93 204 59 04. E-mail address: rtaqam@iiqab.csic.es (R. Tauler). In order to establish separation methodologies and determine phenolic acids in biological samples, liquid chromatography (LC) is at present the method of choice because of its versatility, precision and sensitivity [3–5]. Molecular UV–vis absorption spectroscopy is one of the most useful tools currently employed in the determination of compounds when it is combined with LC. Absorption spectra can be combined with retention param- eters for the possible identification of unknown compounds, to measure purity of the elution band in question and to perform quantitative sample analysis. In this context, mass spectrometry detection is also being used at present as a very powerful tool to perform identification and quantitation of unresolved mixtures of phenolic acids [6]. In this study, the proportion of organic modifier and the pH of the hydro-organic mobile phase are optimized in order to separate a series of nine phenolic acids. Relationships between the retention parameters of the compounds and Reichardt’s E N T scale of solvent polarity have been used to optimize the propor- tion of organic modifier in the mobile phase [7]. Relationships between the capacity factor and the pH measured in the different acetonitrile–water mixtures have also been used to optimize the pH of the mobile phase and pK a values of the studied phenolic 0039-9140/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2006.07.030