Talanta 80 (2009) 212–217 Contents lists available at ScienceDirect Talanta journal homepage: www.elsevier.com/locate/talanta Simultaneous extraction and preconcentration of uranium and thorium in aqueous samples by new modified mesoporous silica prior to inductively coupled plasma optical emission spectrometry determination Seyed Reza Yousefi a , Seyed Javad Ahmadi b,∗ , Farzaneh Shemirani a , Mohammad Reza Jamali c , Masoud Salavati-Niasari d a School of Chemistry, University College of Science, University of Tehran, Tehran, Iran b Jaber Ibne Hayan Research Laboratories, Nuclear Science and Technology Research Institute, Kargar, Tehran, Iran c Department of Chemistry, Payam Noor University, Behshahr, Iran d Department of Chemistry, Faculty of Science, University of Kashan, Kashan, Iran article info Article history: Received 26 March 2009 Received in revised form 23 June 2009 Accepted 25 June 2009 Available online 3 July 2009 Keywords: Preconcentration Determination of uranium and thorium Mesoporous silica (MCM-41) Solid phase extraction (SPE) Inductively coupled plasma optical emission spectrometry (ICP OES) abstract A new synthesized modified mesoporous silica (MCM-41) using 5-nitro-2-furaldehyde (fural) was applied as an effective sorbent for the solid phase extraction of uranium(VI) and thorium(IV) ions from aqueous solution for the measurement by inductively coupled plasma optical emission spectrometry (ICP OES). The influences of some analytical parameters on the quantitative recoveries of the analyte ions were inves- tigated in batch method. Under optimal conditions, the analyte ions were sorbed by the sorbent at pH 5.5 and then eluted with 1.0 mL of 1.0 mol L -1 HNO 3 . The preconcentration factor was 100 for a 100 mL sam- ple volume. The limits of detection (LOD) obtained for uranium(VI) and thorium(IV) were 0.3 gL -1 . The maximum sorption capacity of the modified MCM-41 was found to be 47 and 49 mg g -1 for uranium(VI) and thorium(IV), respectively. The sorbent exhibited good stability, reusability, high adsorption capacity and fast rate of equilibrium for sorption/desorption of uranium and thorium ions. The applicability of the synthesized sorbent was examined using CRM and real water samples. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Uranium and thorium are important elements not only in indus- trial application but also in energy and environmental problems. In view of the extensive usage of uranium and thorium for vari- ous industrial purposes and their toxicity, precise determination of these elements in environmental and biological samples is a chal- lenging task [1–3]. Both of the metal ions are known to cause acute toxicological effects in human and their compounds are poten- tial occupational carcinogens [4]. The WHO, Health Canada and Australian drinking water guidelines fixed the maximum uranium concentration in drinking waters to be less than 9, 20 and 20 gL -1 . Uranium is present in seawater, in concentration of approximately 3 gL -1 [1,5]. The low concentration of these ions in the presence of relatively high concentration of divorce ions makes it difficult to determine directly uranium and thorium ions. So, a separation and preconcen- tration is mandatory prior to their determination by highly versatile ∗ Corresponding author. Tel.: +98 21 880003793. E-mail address: sjahmadi@aeoi.org.ir (S.J. Ahmadi). techniques such as inductively coupled plasma optical emission spectrometry (ICP OES). Many separation and preconcentration techniques for metal ions have been developed such as liquid–liquid extraction [6,7] and solid phase extraction (SPE) [8–18]. Among these methods, SPE was used widely in separation and preconcentration systems. Compared with traditional technologies, SPE offers several advan- tages such as faster, higher enrichment factor, inexpensive and less polluting to the environment [19,20]. In SPE technique, it is impor- tant to select a suitable adsorption material, which can not only enrich the analytes, but also eliminate the matrix interference effec- tively. Several solid phase sorbents such as organic chelating resin [21–25], modified activated carbon [26], modified silica gel [27,28] and polyurethane foam [29–31] have been employed for the sepa- ration and preconcentration of uranium(VI) and thorium(IV). The rapid development of mesoporous materials such as MCM- 41 has attracted much attention in various scientific areas including physics, chemistry and material science. The advantages of large surface area, well-defined pore size, excellent mechanical resis- tance, non-swelling, excellent chemical stability and easy to modify, make the ordered mesoporous materials an ideal supporting mate- rial in SPE. They are synthesized with surfactant used as template. 0039-9140/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2009.06.058