Sensors and Actuators B 133 (2008) 235–240 Contents lists available at ScienceDirect Sensors and Actuators B: Chemical journal homepage: www.elsevier.com/locate/snb New membrane electrodes based on a functionalized tetraphenylborate covalently bound to the polymeric backbone Marco Giannetto ∗ , Alessandra Bello, Marcello Gennari, Luciano Marchi ` o, Giovanni Mori Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Universit` a degli Studi di Parma, Viale G.P. Usberti 17/A, 43100 Parma, Italy article info Article history: Received 29 October 2007 Received in revised form 8 February 2008 Accepted 13 February 2008 Available online 4 March 2008 Keywords: Ion-selective electrode Tetraphenylborate Covalent link abstract In this study new liquid contact polymeric membrane ion-selective electrodes (ISEs) have been real- ized with the aim of reducing leaching phenomena of active component and so improving the shelf life of the electrode. A new tetraphenylborate ion exchanger functionalized with allylic moieties has been synthesized and linked to a copolymer acrylonitrile–butadiene, alternative to PVC. The linking reaction takes place by radicalic mechanism and is catalysed by dicumyl peroxide. The leaching of the so obtained polymers has been evaluated by spectrophotometric and potentiometric measurements to check the effectiveness of the reaction. In order to test the performances of the new polymeric material, ISEs with and without ionophore have been prepared using the functionalized matrix as well as traditional PVC as polymeric membrane. Analysis of variance was carried out on the detection limit and on the slope of the calibration curve obtained for every kind of electrode, in order to identify the effects of the covalently bound ion exchanger on the lifetime and performance of the sensors. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Liquid membrane ion-selective electrodes (ISEs) provide a fast, cheap and relatively versatile analytical approach to samples of environmental, clinical and food processing interest. ISEs can be used very rapidly and easily, under favourable conditions, when measuring ions in relatively dilute aqueous solutions [1,2]. Fur- thermore, they are unaffected by sample colour or turbidity and are suitable for on-line continuous analysis. In the last decades the mistrust of analysts with respect to such devices was almost com- pletely overcome, thanks to the advances achieved in the field of materials and ionophores employed for realization of the mem- branes, leading to a dramatic increase of the commercial diffusion of ISEs [3,4]. Conversely, some limit of potentiometric sensors does persist, like relatively short lifetime of the membrane. Performance of ISE is in fact strongly affected by leaching phenomena of the ionic exchanger and the ionophore from the membrane. Ionic fluxes occurring across the membrane also affect the performance of the sensor in terms of lower detection limit [5,6]. Several strategies have been tested to limit such phenom- ena: different researchers reported about ISEs based on ionophores covalently bound to the membrane polymeric matrix, with the aim ∗ Corresponding author. Tel.: +39 0521 905423; fax: +39 0521 905557. E-mail address: marco.giannetto@unipr.it (M. Giannetto). to reduce ion fluxes [7–9]. Much lower attention has been paid to the improvement of the lifetime. Moreover, a negative effect on the selectivity was sometimes observed as consequence of the immobilization of the active components on the membrane matrix by covalent linking. A considerable amount of studies have been also conducted about innovative materials for realization of the membranes: in 1997 Kim et al. [10] reported about new chloride- selective electrodes based on membranes prepared by sol–gel method. This approach evidenced that the experimental conditions under which the gelation of the starting siloxanes is carried out (acid catalysis and high temperatures) often are incompatible with the ionophores, that undergo chemical decomposition. The use of acrylonitrile–butadiene copolymers, also known with the commercial name Krynac ® , was proposed by Ebdon and co- workers [11,12], that reported about realization of nitrate selective electrodes based on tetraalkylammonium exchanger units bound to the copolymer by means of radicalic linking. In this paper is reported the realization of new membrane ISEs with limited leaching of the lypophilic ionic exchanger. For this purpose Krynac ® was employed as membrane matrix, in order to suit its reactivity for the linking of properly designed and synthe- sized tetraphenylborates, derivatized with allylic functionalities. The study involved the synthesis of the suitable tetraphenylborate, the radicalic linking of the exchanger to the polymeric matrix and the potentiometric characterization of the functionalized mem- branes. 0925-4005/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2008.02.040