Talanta 70 (2006) 257–266 Simultaneous preconcentration of uranium(VI) and thorium(IV) from aqueous solutions using a chelating calix[4]arene anchored chloromethylated polystyrene solid phase V.K. Jain ∗ , R.A. Pandya, S.G. Pillai, P.S. Shrivastav Chemistry Department, School of Sciences, Gujarat University, Ahmedabad 380009, India Received 7 November 2005; received in revised form 12 February 2006; accepted 12 February 2006 Available online 30 March 2006 Abstract A new chelating polymeric sorbent is developed using Merrifield chloromethylated resin anchored with calix[4]arene-o-vanillinsemicarbazone for simultaneous separation and solid phase extractive preconcentration of U(VI) and Th(IV). The “upper-rim” functionalized calix[4]arene-o- vanillinsemicarbazone was covalently linked to Merrifield resin and characterized by FT-IR and elemental analysis. The synthesized chelating polymeric sorbent shows superior binding affinity towards U(VI) and Th(IV) under selective pH conditions. Various physico-chemical parame- ters that influence the quantitative extraction of metal ions were optimized. The optimum pH range and flow rates for U(VI) and Th(IV) were 6.0–7.0 and 1.0–4.0 ml min -1 and 3.5–4.5 and 1.5–4.0 ml min -1 , respectively. The total sorption capacity found for U(VI) and Th(IV) was 48734 and 41175 gg -1 , respectively. Interference studies carried out in the presence of diverse ions and electrolyte species showed quantitative ana- lyte recovery (98–98.5%) with lower limits of detection, 6.14 and 4.29 gl -1 and high preconcentration factors, 143 and 153 for U(VI) and Th(IV), respectively. The uptake and stripping of these metal ions on the resin were fast, indicating a better accessibility of the metal ions towards the chelating sites. The analytical applicability of the synthesized polymeric sorbent was tested with some synthetic mixtures for the separation of U(VI) and Th(IV) from each other and also from La(III), Cu(II) and Pb(II) by varying the pH and sequential acidic elution. The validity of the proposed method was checked by analyzing these metal ions in natural water samples, monazite sand and standard geological materials. © 2006 Elsevier B.V. All rights reserved. Keywords: Merrifield chloromethylated resin; Solid phase extraction; GFAAS; ICPAES; Preconcentration; Calix[4]arene-o-vanillinsemicarbazone 1. Introduction Uranium and thorium find extensive application as nuclear fuel in power plants and their main sources are pitchblende, monazite sand and sea water. Their selective extraction simulta- neously in presence of each other and closely associated metal ions has drawn much attention of the chemists world over because of their importance in energy related applications [1]. The separation of these economically important metal ions is also a matter of concern as the nuclear waste coming out of reactors cause serious and irreversible environmental and bio- logical damage [2]. Both the metal ions are known to cause ∗ Corresponding author. E-mail addresses: drvkjain@hotmail.com (V.K. Jain), rapandya@hotmail.com (R.A. Pandya). acute toxicological effects in mammals and their compounds are potential occupational carcinogens [3]. Thus, there remains a need of preorganized complexing agents that discriminates U(VI) and Th(IV) from associated metal ions present in great excess in solid or aqueous media. The procedures described in the recent literature, for the separation and trace determi- nation of U(VI) and Th(IV) are either less sensitive or time consuming due to high matrix concentration [4–13]. So far, mod- est work has been done towards simultaneous separation and solid phase extractive preconcentration of U(VI) and Th(IV). The reagents available for the separation and trace determina- tion of these metal ions are either less specific as a number of diverse ions interfere during their determination or it may require further purification by ion exchange chromatography [14–20]. A separation and preconcentration is therefore manda- tory ahead of their determination by highly versatile techniques like GFAAS and ICPAES. Solid phase extraction technique has 0039-9140/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2006.02.032