Ionic imprinted polymer for nickel recognition by using the bi-functionalized 5-vinyl-8-hydroxyquinoline as a monomer: Application as a new solid phase extraction support Jacobo Otero-Romaní a , Antonio Moreda-Piñeiro a , Pilar Bermejo-Barrera a, ⁎, Antonio Martin-Esteban b a Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Chemistry, University of Santiago de Compostela, Avenida das Ciencias, s/n. 15782 Santiago de Compostela, Spain b Department of Environment, National Institute for Agriculture and Food Research (INIA), Carretera de A Coruña, Km 7.5, 28040 Madrid, Spain abstract article info Article history: Received 30 June 2009 Accepted 29 July 2009 Available online 8 August 2009 Keywords: Ionic imprinted polymer 5-vynil-8-hydroxyquinoline Nickel Seawater Solid phase extraction A new ionic imprinted polymer (IIP) for Ni(II) recognition/pre-concentration was prepared via precipitation polymerization using 2-(diethylamino) ethyl methacrylate (DEM) and divinylbenzene (DVB) as a cross- linking agent in the presence of nickel(II) and 5-vynil-8-hydroxyquinoline (5-VHQ) as a bi-functionalized ligand. An important increase on the selectivity of the synthesised IIP for nickel(II) ions was obtained when comparing to the use of 8-hydroxyquinoline (8-HQ) as a ligand. The synthesised IIP was used as a new support for solid phase extraction (SPE) of nickel(II) from seawater before inductively coupled plasma optical emission spectrometry (ICP-OES) detection. Variables affecting the SPE process, such as pH, load and elution flow rates, and concentration and volume of the eluting solution, were fully evaluated. The optimised procedure consists of a sample loading (100 mL of seawater at a pH of 9.0 ± 0.1) through IIP-SPE cartridges containing 300 mg of the synthesised IIP at a flow rate of 3.0 mL min -1 . Elution was performed by passing 2.5 mL of 2.0 M nitric acid at a flow rate of 1.5 mL min -1 , which gave a pre-concentration factor of 40. The limit of detection (LOD) of the method was 0.26 μg L -1 , while the relative standard deviation (RSD) for eleven replicated measurements was 3%. Accuracy of the method was assessed by analyzing SLEW-3 (estuarine water) and TM-23.3 (lake water) certified reference materials. In addition to the selectivity of the synthesised material for nickel(II) ions against other transition metal ions and major alkaline and alkaline- earth metals (Na + ,K + , Mg 2+ and Ca 2+ ) in seawater, it can be stated that the salt matrix is efficiently removed by using the proposed IIP-SPE procedure. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Solid phase extraction is one of the most used techniques for isolating trace elements from liquid samples before analytical determinations mainly by atomic spectrometric methods. However, the main disadvantage of conventional SPE sorbents for trace ele- ments, such as C18, ion-exchange resins and size-exclusion phases, is the lack of selectivity, leading to the co-extraction of matrix concomi- tants with the target analytes [1]. This fact is specially important when coping with seawater samples because of the high salt content which is an important source of spectral and matrix interferences [2–4]. However, specific SPE sorbents, as immunosorbents (ISs) and molecu- larly imprinted polymers (MIPs), can avoid this problem by providing selective extraction of such analytes [5]. Synthetic MIPs offer artificial recognition sites which are able to specifically rebind a target molecule in the presence of other similar compounds. These materials can be easily prepared by polymerization of functional and crosslinking monomers around a template molecule (target). As result, a highly cross-linked three-dimensional network polymer is obtained. After polymerization, the template molecule is leached, and the polymer offers binding sites with shape, size and functionalities complementary to the target analyte [6]. Most of the MIPs are prepared by bulk polymerization. After this polymerization process, the material obtained has to be ground and sieved to obtain certain uniformity in particle size. These stages commonly lead to loses of fine particles of the synthesised material. In addition, the particles obtained are normally irregular in size and shape, and some binding sites are partially destroyed during grinding which leads to a considerable loss of loading capacity of the imprinted polymer [7]. To overcome these problems, different polymerization methods (suspension, emulsion, dispersion and precipitation) have been proposed for synthesising MIPs [8]. These synthesis techniques have emerged as appealing methods for producing high-quality imprinted products [9–11], because crushing and sieving steps are avoided and higher yields of reaction are obtained. IIPs are similar to MIPs but they recognize metal ions after imprinting. For the last years different IIPs have been synthesised for Microchemical Journal 93 (2009) 225–231 ⁎ Corresponding author. Tel.: +34 600942346. E-mail address: pilar.bermejo@usc.es (P. Bermejo-Barrera). 0026-265X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.microc.2009.07.011 Contents lists available at ScienceDirect Microchemical Journal journal homepage: www.elsevier.com/locate/microc