Talanta 78 (2009) 523–529 Contents lists available at ScienceDirect Talanta journal homepage: www.elsevier.com/locate/talanta Ion-imprinted polymethacrylic microbeads as new sorbent for preconcentration and speciation of mercury Ivanka Dakova ∗ , Irina Karadjova, Ventsislava Georgieva, George Georgiev Department of Chemistry, Sofia University, Sofia, Bulgaria article info Article history: Received 17 April 2008 Received in revised form 30 November 2008 Accepted 2 December 2008 Available online 7 December 2008 Keywords: Solid phase extraction Ion-imprinted polymer Hg Inorganic mercury Cold vapor atomic absorption spectrometry abstract Metal ion-imprinted polymer particles have been prepared by copolymerization of methacrylic acid as monomer, trimethylolpropane trimethacrylate as cross-linking agent and 2,2 ′ -azobisisobutyronitrile as initiator, in the presence of Hg(II)-1-(2-thiazolylazo)-2-naphthol complex. The separation and preconcen- tration characteristics of the Hg-ion-imprinted microbeads for inorganic mercury have been investigated by batch procedure. The optimal pH value for the quantitative sorption is 7. The adsorbed inorganic mer- cury is easily eluted by 2 mL 4 M HNO 3 . The adsorption capacity of the newly synthesized Hg ion-imprinted microbeads is 32.0 mol g -1 for dry copolymer. The selectivity of the copolymer toward inorganic mer- cury (Hg(II)) ion is confirmed through the comparison of the competitive adsorptions of Cd(II), Co(II), Cu(II), Ni(II), Pb(II), Zn(II)) and high values of the selectivity and distribution coefficients have been calcu- lated. Experiments performed for selective determination of inorganic mercury in mineral and sea waters showed that the interfering matrix does not influence the extraction efficiency of Hg ion-imprinted microbeads. The detection limit for inorganic mercury is 0.006 gL -1 (3), determined by cold vapor atomic adsorption spectrometry. The relative standard deviation varied in the range 5–9 % at 0.02–1 gL -1 Hg levels. The new Hg-ion-imprinted microbeads have been tested and applied for the speciation of Hg in river and mineral waters: inorganic mercury has been determined selectively in nondigested sample, while total mercury e.g. sum of inorganic and methylmercury, has been determined in digested sample. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Due to the high toxicity and accumulative character of mercury, the determination of trace amounts of this element in environ- mental samples is an actual analytical task. For mercury in natural waters, the main species to be identified and determined, are inorganic mercury (Hg(II)) and methylmercury (CH 3 Hg(I)). Recent reports estimate a total mercury concentration in natural waters ranging from 0.2 to 100 ng L -1 [1], while methylmercury levels are much lower (ca. 0.05 ng L -1 ) [2]. Highly sensitive methods are required for direct determination of such extremely low levels and most frequently accurate and reliable results for Hg-species con- tent in natural waters have been achieved after suitable separation and preconcentration step. A great variety of analytical proce- dures for Hg(II) preconcentration and separation, based mainly on liquid–liquid extraction [3–5], coprecipitation [6,7], and solid phase extraction (SPE) [8–16] have been proposed. The SPE procedures as separation and preconcentration methods exhibit numerous advantages such as flexibility, high preconcentration factors, high retention capacity, speed and simplicity, possibilities for field sam- ∗ Corresponding author. Tel.: +3592 81 61 244. E-mail address: i.dakova@chem.uni-sofia.bg (I. Dakova). pling, ease of automation [17]. However, it should be noted that the extraction efficiency and selectivity of this technique is strongly dependent on the sorbent material used. Therefore, the develop- ment of new adsorbents with high affinity and specific recognition for Hg(II) or CH 3 Hg(I) ion is of great interest. During the last years ion-imprinted polymers (IIPs), as selec- tive sorbents for a particular chemical form of the given element, have received much attention. The high selectivity of IIPs can be explained by the polymer memory effect toward the metal ion interaction with a specific ligand, coordination geometry, metal ion coordination number, charge and size [18]. Numerous studies on IIPs and their application for selective preconcentration and sep- aration of metal ions have been reported lately [19–28] including Hg(II)-imprinted ones [29–32]. Due to the high toxicity and accu- mulative character of the mercury species the synthesis of sorbents for mercury preconcentrative separation in water samples is of spe- cial interest. In the present paper we report the synthesis of polymer microbeads using methacrylic acid (MAA) as a monomer, trimethy- lolpropane trimethacrylate (TMPTM) as a cross-linking agent, and 1-(2-thiazolylazo)-2-naphthol (TAN) as a specific ligand for Hg(II). The extraction characteristics of the non-imprinted (blank P(B)), treated with TAN alone (control P(TAN)), and imprinted with Hg(II)-TAN complex (P(TAN-Hg)) polymer microbeads have been 0039-9140/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2008.12.005