PAPER IN FOREFRONT Surfactant-coated carbon nanotubes for the liquid–liquid extraction of phthalates and other migrants in virgin olive oils Silvia López-Feria & Rafael Lucena & Soledad Cárdenas & Miguel Valcárcel Received: 12 May 2009 / Revised: 9 August 2009 / Accepted: 11 August 2009 / Published online: 4 September 2009 # Springer-Verlag 2009 Abstract This article presents a novel application of the surfactant-coated carbon nanotubes for the joint extraction of phthalates, xylene isomers and styrene from virgin olive oils. For this purpose, two carbon nanotubes, multi-walled and single-walled carbon nanotubes, were evaluated, the former providing the better results. The target migrants were liquid–liquid extracted from the virgin olive oil samples by means of the carbon nanotube pseudophase, and the aqueous extracts were analysed by headspace-gas chromatography-mass spectrometry. Sodium chloride was added to favour the release of the analytes to the gaseous phase of the vial. The comparison of the chromatograms obtained with the direct analysis reveals a sensitivity enhancement with the use of the surfactant-coated carbon nanotubes, especially for the phthalates, which can be ascribed to the π–π interaction between the aromatic ring and the nanotube surface. Limits of detection were between 6 and 30 μgL -1 for 1 mL of sample. The precision of the method was better than 7.6% and the recoveries higher than 92%. Finally, the influence of the package material and the storage conditions on the concentration of the analytes was accomplished, and it was found that the concentration of phthalates increases with time in all the packages studied, while the more volatile compounds were found to decrease under the same conditions. Keywords Phthalates . Xylene isomers . Styrene . Liquid–liquid extraction . Carbon nanotubes . Headspace-gas chromatography-mass spectrometry Introduction Phthalic acid esters, commonly called phthalates, are widely used (about 80% of these compounds) as plastizicers in the polymer industry to improve flexibil- ity, workability and general handling properties. Since these compounds do not form stable bonds with polymer to which they are added, these substances tend to migrate from the package to the product contained in it, especially in the case of fatty and oily foodstuffs, so becoming contaminants. Because of their extensive use, they are potential hazards for human health as a consequence of their endocrine disruptive effects [1, 2]. Regarding xylene isomers (ortho, meta and para) and styrene, all are volatile aromatic hydrocarbons that can appear either naturally (viz. superior plant wax, natural oil seepage, amino acid fermentation) or by anthropogenic sources (viz. combustion products, industrial paints, adhesives, packages). Their lipophilic nature makes them also especially harmful by accumulation in fatty foodstuffs and concretely edible oils and fats, and their effects comprise changes in the liver to damages in heart and nervous system, among others [3, 4]. With the aim of preserving health safety, a substantial amount of research effort is being undertaken in order to monitor the level of contamination in different types of foods directly in contact with materials made up of these compounds, mainly plasticised packages. Most of them involve gas chromatography coupled to several detectors. For matrices with high fat contents, it is necessary to S. López-Feria CIFA Venta del Llano, IFAPA, Ctra. Bailén-Motril km 18.5 Mengíbar, 23620 Jaén, Spain R. Lucena : S. Cárdenas : M. Valcárcel (*) Department of Analytical Chemistry, University of Córdoba, Marie Curie Building (Annex), Campus de Rabanales, Cordoba 14071, Spain e-mail: qa1meobj@uco.es Anal Bioanal Chem (2009) 395:737–746 DOI 10.1007/s00216-009-3066-4