Journal of Chromatography A, 1227 (2012) 29–37 Contents lists available at SciVerse ScienceDirect Journal of Chromatography A jou rn al h om epage: www.elsevier.com/locat e/chroma A novel in situ preconcentration method with ionic liquid-based surfactants resulting in enhanced sensitivity for the extraction of polycyclic aromatic hydrocarbons from toasted cereals Mónica Germán-Hernández a,1 , Verónica Pino a,∗ , Jared L. Anderson b,2 , Ana M. Afonso a,3 a Departamento de Química Analítica, Nutrición y Bromatología, Universidad de La Laguna (ULL), La Laguna (Tenerife) 38206, Spain b Department of Chemistry, The University of Toledo, Toledo, OH 43606, USA a r t i c l e i n f o Article history: Received 15 November 2011 Received in revised form 22 December 2011 Accepted 23 December 2011 Available online 8 January 2012 Keywords: Ionic liquids Ionic liquid-based surfactants Polycyclic aromatic hydrocarbons High-performance liquid chromatography Fluorescence detection Microwave-assisted extraction Food samples a b s t r a c t A preconcentration procedure utilizing IL-based surfactants it is described for the first time. The procedure is based on transforming a water-soluble IL-based surfactant, 1-hexadecyl-3- butylimidazolium bromide (C 16 C 4 Im-Br), into a water-insoluble IL, 1-hexadecyl-3-butylimidazolium bis[(trifluoromethane)sulfonyl]imide (C 16 C 4 Im-NTf 2 ), via a simple metathesis reaction. The preconcen- tration procedure is used in combination with a micellar microwave-assisted extraction (MMAE) method for the analysis of sixteen polycyclic aromatic hydrocarbons (PAHs) from toasted cereals. The obtained microdroplet of C 16 C 4 Im-NTf 2 containing the extracted PAHs is then diluted with acetonitrile and injected into a high-performance liquid chromatograph (HPLC) employing UV–vis and fluorescence detection. This in situ preconcentration step highly improves the sensitivity of the MMAE despite the complexity of the solid matrix. The developed in situ preconcentration method exhibited almost quantitative extraction efficiencies (80–95% in average) for the PAHs studied, and good precision values (lower than 14%). The overall MMAE + in situ preconcentration method presented limits of detection down to 0.03 g kg -1 . © 2012 Elsevier B.V. All rights reserved. 1. Introduction The determination of trace analytes in complex solid matrixes is a serious challenge for analytical chemists. This becomes more difficult when the elimination (or minimization) of hazardous sub- stances such as organic solvents in the analytical extraction step is intended. New trends are focused on utilizing more benign extrac- tion solvents as well as microextraction procedures [1,2]. Surfactants have been widely used in the analytical extraction of hydrophobic analytes contained in solids as they provide an alter- native to organic solvents. They are often coupled with microwaves in micellar microwave-assisted extraction (MMAE) to increase the extraction kinetics [3,4]. The micellar extract containing the ana- lytes of interest can normally be subjected to high-performance liquid chromatographic (HPLC) separation without the need of ∗ Corresponding author. Tel.: +34 922318990; fax: +34 922318003. E-mail addresses: mogerman@ull.es (M. Germán-Hernández), veropino@ull.es (V. Pino), Jared.Anderson@utoledo.edu (J.L. Anderson), aafonso@ull.es (A.M. Afonso). 1 Tel.: +34 922 845200; fax: +34 922318090. 2 Tel.: +1 4195301508; fax: +1 4195304033. 3 Tel.: +34 922318039; fax: +34 922318090. additional clean-up steps. However, this approach lacks sensitivity due to the fact that there is no preconcentration step. Several strategies have been carried out to improve the detection limits of MMAE. For example, the preconcentration of non-ionic micellar extracts can be conducted by cloud-point extraction (CPE) [5]. In this approach, aqueous solutions of non- ionic surfactants (at concentrations above the critical micelle concentration) become turbid at a temperature known as the cloud point, above which there is a separation of the solution into two phases; namely, a small volume of a concentrated phase which contains the majority of the surfactant (V s ), and a high volume of a diluted phase which contains low amounts of surfactant (V aq ). Analytes that are preconcentrated in the surfactant-rich phase (V s ) can be injected directly into HPLC. Cationic surfactants do not exhibit cloud-point behavior unless high acidic conditions or high ionic strengths are employed [6,7]. The development of preconcentration methods employing cationic surfactants without the requirement of such extreme conditions is of interest, and in this sense, several authors have proposed the mixing of cationic surfactants with nonionic or anionic surfactants to favor their cloud-point [8,9]. Ionic liquids (ILs) are non-molecular solvents possessing low melting points and a wide variety of interesting properties [10]. Their use and application in separation science has increased 0021-9673/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.chroma.2011.12.097