Analytical Methods Determination of phenolic and other polar compounds in flaxseed oil using liquid chromatography coupled with time-of-flight mass spectrometry Wahid Herchi a,⇑ , Saleh Sawalha b , David Arráez-Román b , Sadok Boukhchina a , Antonio Segura-Carretero b , Habib Kallel a , Alberto Fernández-Gutierrez b a Laboratoire de Biochimie des Lipides, Département de Biologie, Faculté des Sciences de Tunis, 2092 ELmanar, Tunisia b Department of Analytical Chemistry, Faculty of Sciences, University of Granada, C/Fuentenueva s/n, 18071 Granada, Spain article info Article history: Received 24 March 2010 Received in revised form 9 October 2010 Accepted 13 October 2010 Keywords: HPLC–ESI–TOF (MS) Phenolic compounds Flaxseed oil Lignans abstracttabstract A new method based on high-performance liquid chromatography coupled with electrospray ionisation time-of-flight-mass spectrometry (HPLC–ESI–TOF (MS)) has been used to analyse phenolic compounds in flaxseed oil. Some phenolic compounds such as secoisolariciresnol, ferulic acid and its methyl ester, cou- maric acid methyl ester, diphyllin, pinoresinol, matairesinol, p-hydroxybenzoic acid, vanillin and vanillic acid have been detected from flaxseed oil. The quantification of these compounds in three varieties of flaxseed oils was carried out using their commercial standards. The efficiency, rapidity and high resolu- tion of HPLC coupled to the sensitivity, selectivity, mass accuracy and true isotopic pattern from TOF (MS) have revealed an enormous separation potential allowing the determination of a broad series of phenolic and other polar compounds present in flaxseed oil for the first time. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Flaxseed oil has been gaining popularity in the health food mar- ket because of its reported health benefits and disease preventive properties on coronary heart disease, some kinds of cancer and neurological and hormonal disorders (Oomah & Mazza, 2000). Dur- ing the last decade, there has been an increasing interest in the use of flaxseed oil in the diet in order to improve the nutritional and health status (Oomah, 2001). Flaxseed oil is rich in lignans with high omega-3 fatty acid content (Westcott & Muir, 2003). The ben- eficial effects of lignans on human health are well recognised (McCann, Gill, Mc Glynn, & Rowland, 2005). Other phenolic com- pounds of interest that are accumulated in flaxseed oil include ferulic and vanillic acid (Siger, Nogala-Kalucka, & Lampart-Szczapa, 2008). The qualitative and quantitative determination of the phenolic compounds in oil is very important and several methods have been already used in recent years (Carrasco-Pancorbo, Neu- süß, Pelzing, Segura-Carretero, & Fernández-Gutiérrez, 2007; Weisz, Kammerer, & Carle, 2009). Various methods have been reported for the identification of these substances in flaxseed starting from the early days, non-spe- cific analytical methods, such as paper, thin-layer (Coran, Giannel- lini, & Bambagiotti-Alberti, 2004), and column chromatography as well as UV spectroscopy, were applied to polyphenols analysis (Christophoridou, Dais, Tseng, & Spraul, 2005). The need to identify individual phenolic compounds meant that traditional methods were replaced and significant progress was achieved when more specific analytical techniques were used, such as gas chromatogra- phy (GC) (Penalvo, Haajanen, Botting, & Adlercreutz, 2005) or high- performance liquid chromatography (HPLC) (Charlet et al., 2002). The results obtained by using GC are very reliable and interesting, but the use of this technique is less common because the derivat- isation step is essential and the use of high temperature which could damage this kind of analytes. HPLC hyphenated to Mass Spectrometry (MS) detection is one of the most important analyt- ical techniques used for the analysis of phenolic compounds (Carr- asco-Pancorbo et al., 2007). The advantages of MS detection include the ability to determine the accurate mass and to obtain structural information (Carrasco-Pancorbo et al., 2005). The deter- mination of the phenolic compounds in flaxseed has been carried out by other research groups (Eliasson, Kamal-Eldin, Andersson, & Aman, 2003; Tanja & Gerhard, 2002) however, it is the first time in which phenolic compounds from flaxseed are identified and quantified using HPLC–ESI–TOF (MS). We describe here a simple HPLC–ESI–TOF (MS) method to analyse phenolic and other polar compounds in oil samples after solid-phase extraction. Our pro- posed method is useful as it permits to identify and quantify 10 compounds which are relevant in flaxseed oil and other oils. 2. Materials and methods 2.1. Chemicals and reagents All chemicals were of analytical reagent grade and used as re- ceived. The organic solvents, hexane, methanol and ACN, used in 0308-8146/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2010.10.070 ⇑ Corresponding author. Tel.: +216 96538999; fax: +216 76678080. E-mail address: wahid1bio@yahoo.fr (W. Herchi). Food Chemistry 126 (2011) 332–338 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem