Indian Journal of Chemistry Vol. 49A, October 2010, pp. 1325-1331 A dynamic electrochemical sensor for europium(III) Sonika Tyagi a , Himanshu Agarwal b & Saiqa Ikram a a Department of Chemistry, Faculty of Natural Science, Jamia Millia Islamia (Central University), New Delhi 110 025, India Email: saiqa.ch@jmi.ac.in b Department of Chemistry, LRPG College, Sahibabad, Ghaziabad 201 015, India Received 27 January 2010 revised and accepted 21 September 2010 A new calixarene derivative, i.e., p-tert-butylcalix[4]arene has been used as an excellent ionophore in the construction of a novel PVC based Eu(III)-selective electrode. A master membrane with percentage composition of PVC:DBP:L: NaTPB:: 32:55:4:9 gives the best results. The membrane electrode exhibits a nernstian response with the slope of 19.7±1.0 mV/decade over a wide concentration range of 9.1 × 10 -8 -1.0 × 10 -1 M and with detection limit of 8.8 × 10 -8 M. The effects of membrane composition and pH as well as the influence of the anionic additive on the electrode performance have been investigated. The potential response of the resulting sensor is not influenced in the pH range 3.0-9.0. Moreover, the membrane electrode has a good reproducibility (RSD 3%), very fast response time (5 s) and ability to detect Eu(III) among other rare earth metal and common cations. The membrane sensor works satisfactorily up to 40% non-aqueous medium and can be used over a period of 6 months. The sensor has been successfully applied for the determination of Eu(III) in analytical and biological samples (urine and serum) and also acts as an electrode indicator. Keywords: Electrochemistry, Sensors, Calixarenes, Europium The last few years have seen growing interest in inorganic and bioorganic chemistry of rare earths because of their wide industrial applications. Their determination is necessary due to toxicity and other adverse effects 1 . There are several applications reported for lanthanides, especially europium, which has been used to dope some types of glass to make lasers. Europium complexes are also used for differentiating between genuine and counterfeit currency notes 2 . Europium phosphors are used in television tubes to give a bright red colour and as an activator for yttrium-based phosphors. For powerful street lighting a small amount of europium is added to mercury vapour lamps to give a more natural light. A salt of europium is used for newer phosphorescent powder and paints. However, europium in dust form is a fire and explosion hazard. Around 400 tons of europium are produced worldwide each year 2,3 . Voltammetry, mass spectroscopy and Rutherford back-scattering techniques, higher order derivative spectrometry, ICP-MS, NAA (neutron activation analysis) and spectrofluorometric methods have been used for the analysis of europium 4-7 . These methods are either time consuming, involving multiple sample manipulations or too expensive for most analytical laboratories. But the potentiometric polymeric electrodes, offer several advantages such as fast and ease of preparations and procedures, simple instrumentations, relatively fast responses, very low detection limit, wide dynamic ranges, reasonable selectivity and low costs. This has led to an increase in the number of available electrodes and microelectrodes over the last few years 8 . However, there are only a few reports available on the europium-selective electrodes in the literature i.e., calix[4]arenetetraphos- phineoxide 9 , N,N-diethyl-N-(4-hydroxy-6-methylpyridin- 2-yl)guanidine 10 , S-N hexadentates Schiff base 11 , 4-(2-hydroxybenzylideneamino)-6-methyl-3-thioxo-3,4- dihydro-1,2,4-triazin-5(2H)-one 12 and 4E-4-(2-(CE)- (2-aminoethylimino)methyl)phenyl 13 . In the proposed work, we have used p-tert-butylcalix[4]arene derivative (L) as a suitable lipophilic neutral ionophore for the construction of a O O O O P P P P Me Me Me Me O O O O Me Me Me Me p-tert-Butylcalix[4]arene derivative (L)