Journal of Chromatography A, 1348 (2014) 71–79 Contents lists available at ScienceDirect Journal of Chromatography A j o ur na l ho me page: www.elsevier.com/locate/chroma Evaluation of magnetic nanoparticles to serve as solid-phase extraction sorbents for the determination of endocrine disruptors in milk samples by gas chromatography mass spectrometry Maria-Evangelia S. Synaridou 1 , Vasilios A. Sakkas ∗ , Constantine D. Stalikas 2 , Triantafyllos A. Albanis 3 Laboratory of Analytical Chemistry, Department of Chemistry, University of Ioannina, Ioannina 45110, Greece a r t i c l e i n f o Article history: Received 12 February 2014 Received in revised form 10 April 2014 Accepted 26 April 2014 Available online 2 May 2014 Keywords: Magnetic solid-phase extraction Magnetite octadecylsilane nanoparticles Milk Organochlorine pesticides Polychlorinated biphenyls Experimental design a b s t r a c t A rapid magnetic solid-phase extraction (MSPE) is proposed based on C18-functionalized magnetic silica nanoparticles as sorbents, for the determination of endocrine disruptors – 20 organochlorine pesticides and 6 polychlorinated biphenyls – in milk samples. Magnetic nanoparticles are characterized by sev- eral techniques, such as Scanning Electron Microscopy, X-Ray diffraction, Brunauer–Emmett–Teller and Fourier transform-infrared. The MSPE is performed by dispersion of the Fe 3 O 4 @SiO 2 @C18 nanoparticles in milk samples with sonication, after protein precipitation. Then, the sorbent is collected by apply- ing an external magnetic field and the analytes are desorbed by n-hexane. Several parameters affecting the extraction efficiency of target analytes by the magnetic nanoparticles are investigated, including washing and elution solvents, amount of sorbents, time of extraction and elution, sample and elution solvent volume. The proposed method is optimized by means of experimental design and response sur- face methodology. When coupled with gas chromatography–mass spectrometry detection and under optimum extraction conditions, average recoveries of target analytes are found to be in the range of 79% to 116%. The proposed MSPE–GC–MS analytical method has a linear calibration curve for all target ana- lytes with coefficients of determination to range from 0.9950 to 0.9999. The limits of quantification are found to be between 0.2 and 1 g/L ensuring compliance with the maximum residue limits established by European Commission and Codex Alimentarius, for OCPs and PCBs residues in milk. The proposed method is applied to the determination of target analytes in milk samples from local markets. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Exposure to endocrine disruption chemicals (EDCs) has become lately a predominant issue in environmental science research and policy, receiving increased public attention. Recently, the U.S. EPA released a much anticipated draft list of compounds to screen for endocrine disruption [1]. The EDCs refer to those compounds that can mimic or block the actions of natural hormones in living organisms and impair their normal functioning, such as growth, metabolism and reproduction [2]. European Commission has also ∗ Corresponding author. Tel.: +30 26510 08303; fax: +30 26510 08796. E-mail addresses: msynarid@cc.uoi.gr (M.-E.S. Synaridou), vsakkas@cc.uoi.gr (V.A. Sakkas), cstalika@cc.uoi.gr (C.D. Stalikas), talbanis@cc.uoi.gr (T.A. Albanis). 1 Tel: +30 26510 08399. 2 Tel: +30 26510 08414. 3 Tel: +30 26510 08363. published a draft list of chemicals, which are believed to damage health by interfering with the way hormones work [3–5]. Organochlorine pesticides (OCPs) have been extensively used as pesticides in agriculture, while polychlorinated biphenyls (PCBs) have been employed as industrial fluids mainly in transformers, capacitors, papers and paints industry. Both groups of compounds are highly lipophilic, chemically stable and resistant to environ- mental degradation, while they are included in relevant lists, as having potential or suspected endocrine activity. However, although these chemicals were banned more than 30 years ago and no longer used, they are globally spread into the environment and may be routinely detected in surface waters, air, fish, wildlife, food and even humans [2,6–12]. Cow’s milk is a major constituent of the daily diet, principally for vulnerable groups such as infants, school age children and elderly. Due to their lipophilic properties, OCPs and PCBs are primarily stored in fat-rich tissues [13] and subsequently translocated and excreted through milk fat [14]. Thus, knowledge of cow’s milk http://dx.doi.org/10.1016/j.chroma.2014.04.092 0021-9673/© 2014 Elsevier B.V. All rights reserved.