Please cite this article in press as: L. Rajski, et al., J. Chromatogr. A (2013), http://dx.doi.org/10.1016/j.chroma.2013.06.070 ARTICLE IN PRESS G Model CHROMA-354469; No. of Pages 12 Journal of Chromatography A, xxx (2013) xxx–xxx Contents lists available at SciVerse ScienceDirect Journal of Chromatography A jou rn al hom epage: www.elsevier.com/locate/chroma Determination of pesticide residues in high oil vegetal commodities by using various multi-residue methods and clean-ups followed by liquid chromatography tandem mass spectrometry Lukasz Rajski a,b , Ana Lozano a , Ana Uclés a , Carmen Ferrer a , Amadeo R. Fernández-Alba a,∗ a Pesticide Residue Research Group, European Union Reference Laboratory (EURL), Department of Hydrogeology and Analytical Chemistry, University of Almería, Ctra. Sacramento S/N ◦ , La Ca˜ nada de San Urbano, 04120, Almería, Spain b Institute of General and Ecological Chemistry. Technical University of Lód´ z, ˙ Zeromskiego 116, 90-924 Lód´ z, Spain a r t i c l e i n f o Article history: Received 26 April 2013 Received in revised form 24 June 2013 Accepted 26 June 2013 Available online xxx Keywords: LC–MS/MS High oil matrices Multiresidue methods Pesticides analysis a b s t r a c t Several extraction methods were evaluated in terms of recoveries and extraction precision for 113 pesti- cides in avocado: QuEChERS with various d-SPE clean-ups (Z-Sep, Z-Sep+, PSA + C18 and silica), miniLuke and ethyl acetate. Extracts were analysed using liquid chromatography coupled with triple quadrupole mass spectrometer working in multi-reaction monitoring mode. Z-Sep and Z-Sep+ are new types of material for high lipid matrices – these two sorbents contain ZrO 2 , which improves fat removal from the extracts. The QuEChERS protocol with Z-Sep provided the highest number of pesticides with recoveries in the 70–120% range along with the lowest amount of coextracted matrix compounds. Subsequently, this method was validated in two matrices – avocado and almonds. In the validation recoveries at two levels – 10 and 50 g/kg – limit of quantitation, linearity, matrix effects, as well as the inter- and intraday precision were studied. In the avocado samples, 107 analytes had LOQs equal to 10 g/kg (signal to noise of quantitative transition was equal 20 or more). In the almond samples, 92 pesticides had LOQs equal to 10 g/kg (S/N ≥ 20) and 2 pesticides at 50 g/kg. The validated method was employed in the analysis of real avocado and almond samples. © 2013 Published by Elsevier B.V. 1. Introduction Pesticide analysis of commodities containing high amounts of lipids produces more difficulties than low or non-fatty matrices. The main problem is in obtaining an extract which contains the target analytes but no fat [1,2]. Representative commodities with high oil content are avocado and almonds. Avocado contains up to 30% fat. The major compo- nents of avocado fat are fatty acids (oleic, palmitic and linoleic) and triglycerides [3]. The oil content in almonds is higher, at around 50%. The major fatty acids present in almonds are the same as those in avocado [4]. Before injecting into the LC system, it is imperative to remove as much as possible of the fat because any fat presence in the sam- ple may influence chromatographic separation [5]. The amount of fat in the final extract depends on the extraction solvent as well as on the clean-up procedure applied. Lipids are readily soluble in solvents such as ethyl acetate, n-hexane or diethyl ether [6]. To limit fat transfer into the extract, a better choice is ∗ Corresponding author. Tel.: +34 950 015 034. E-mail address: amadeo@ual.es (A.R. Fernández-Alba). acetonitrile – nevertheless, a certain amount of lipids may still find their way into the extract. Moreover, acetonitrile may be an inefficient extraction solvent for lipophilic pesticides because these compounds remain in undissolved fat [7]. Likewise, methanol, as a polar solvent, is not good for lipophilic substances [6] – which may be the reason for the low recoveries of some pesticides [2]. The most common methods for fat removal from extract are low temperature precipitation (freezing-out), gel permeation chromatography (GPC) and adsorption (dispersive solid-phase extraction, solid-phase extraction). Freezing-out is the simplest method for fat removal from the extract. Fat is precipitated in the freezer and subsequently separated by centrifugation. Unfor- tunately, this method is time consuming and does not remove all the fat so usually some further clean-up is necessary [8,9]. Gel per- meation chromatography helps to separate low molecular mass compounds, such as pesticides, from high molecular mass com- pounds, such as lipids [10]. However, some pesticides have high molecular mass (e.g. pyrethroids) and cannot be separated from lipids with GPC [11]. Some authors have found GPC to be the best clean-up method for high oil samples [11], whereas others obtained better results with d-SPE [9]. In column SPE and d-SPE clean- up, similar sorbents can be applied: C18 [7–9,12], PSA [7,8,12,13], Florisil [8], Oasis HLB [14,15] and GCB [8,13]. 0021-9673/$ – see front matter © 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.chroma.2013.06.070