Journal of Chromatography A, 1216 (2009) 7346–7350 Contents lists available at ScienceDirect Journal of Chromatography A journal homepage: www.elsevier.com/locate/chroma One step carbon nanotubes-based solid-phase extraction for the gas chromatographic–mass spectrometric multiclass pesticide control in virgin olive oils S. López-Feria a , S. Cárdenas b , M. Valcárcel b,∗ a CIFA Venta del Llano, IFAPA, Ctra. Bailén-Motril km 18.5 Mengíbar, E-23620 Jaén, Spain b Department of Analytical Chemistry, Marie Curie Building (Annex), Campus de Rabanales, University of Córdoba, E-14071Córdoba, Spain article info Article history: Available online 26 February 2009 Keywords: Carbon nanotubes Pesticides Virgin olive oil Solid-phase extraction Gas chromatography–mass spectrometry Quality control abstract This article presents a novel application of carbon nanotubes for the determination of pesticides (chlor- toluron, diuron, atrazine, simazine, terbuthylazin-desethyl, dimetoathe, malathion and parathion) in virgin olive oil samples. For this purpose, two carbon nanotubes, multi-walled and carboxylated single- walled, were evaluated, the later being the most appropriate for the aim of the work. The sorbent (30 mg) was packed in 3-mL commercial cartridge and the virgin olive oil samples diluted (20%, v/v) in hexane were passed through it. After a washing step with 3mL of hexane to remove the sample matrix, the pesticides were eluted with 500 L of ethyl acetate. In order to achieve lower detection limits, the elu- ent was evaporated under a nitrogen stream and the residue reconstituted in 50 L of the same solvent. Aliquots of 2 L of the extract were directly injected into the GC–MS system for analysis. The low limits of detection achieved, between 1.5 and 3.0 gL -1 , permit the application of the method to control the presence of these pollutants in very restrictive samples such as the ecological virgin olive oil. In addition to the sensitivity enhancement, the solid-phase extraction procedure is rather simple as it involves a single preconcentration–elution step, which allows sample processing in less than 8min. Moreover, the cartridge can be reused at least 100 times without losing performance. The method was applied to the determination of the pesticides in two monovarietal and one ecologic commercial extra virgin olive oil samples. Two pesticides were detected in each of the monovarietal virgin olive oils while the ecological sample resulted to be a pesticide-free one. © 2009 Elsevier B.V. All rights reserved. 1. Introduction The increasing production and application of pesticides for agri- cultural purposes has caused the pollution of the environment (soils, waters and air) involving a serious risk to human and liv- ing organisms health by either direct exposure or through residues in foods and drinking waters. In this scenario, alarming levels of pesticides have been reported in air, water or foods, among others [1–3]. For this reason, simplest, reliable methodologies for rapid detection of pesticides are mandatory. Modern trends in analyti- cal chemistry are towards the simplification and miniaturization of sample preparation, as well as the decrease of the organic solvent volume used. In this context, several novel extraction techniques are being developed in order to reduce the analysis step, increase the sample throughput and improve the quality and the sensitivity of analytical methods [4]. ∗ Corresponding author. Tel.: +34 957 218 616; fax: +34 957 218 616. E-mail address: qa1meobj@uco.es (M. Valcárcel). Concerning food control analyses, development of sample- treatment procedures for the isolation of pesticides in matrices with relatively high fat content, such as olive oil and olives, is rather complicated [5]. The preparation of these samples for the determi- nation of pesticides by chromatographic techniques requires the complete removal of the high molecular-mass fat to preserve the separation performance of the chromatographic column. For this reason, an additional cleanup step is usually included in these methods. The most used sample-treatment procedures, includ- ing liquid–liquid extraction (LLE), gel-permeation chromatography (GPC), solid-phase extraction (SPE), matrix solid-phase dispersion (MSPD) or quick, easy, cheap, effective, rugged and safe (QuEChERS) techniques, have been recently reviewed [6]. One example of MSPD treatment was developed for the quantification of a selected group of the most common pesticides employed in olive grove, but the procedure required a previous liquid–liquid extraction step in the olive oil samples [7]. In other case, a multiresidue method was opti- mized using a hexane/acetonitrile extraction with a cleanup step by GPC [8] which was followed by gas chromatographic–tandem mass spectrometric determination. A solid-phase microextraction (SPME) approach was also carried out as a screening method 0021-9673/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.chroma.2009.02.060