Send Orders for Reprints to reprints@benthamscience.ae Current Analytical Chemistry, 2015, 11, 29-35 29 A Novel Iron(III)-Selective Membrane Potentiometric Sensor Based on 5-Chloro-3-[4-(trifluoromethoxy) phenylimino] Indolin-2-one Ersin Demir 1 *, Barıs Kemer 2 Olcay Bekircan 2 and Hassan Y. Aboul-Enein 3, ** ,# 1 Okan University, Vocational School of Health Services, Perfusion Techniques, 34959, Istanbul, Turkey; 2 Karadeniz Technical University, Faculty of Science, Department of Chemistry, 61100, Trabzon, Turkey; 3 Pharmaceutical and Medicinal Chemistry Department, Pharmaceutical and Drug Industries Research Division, National Research Centre, Dokki, Cairo 12311, Egypt Abstract: A novel polyvinyl chloride (PVC) membrane sensor that is highly selective to Fe 3+ ions was prepared by using 5-chloro-3-[4-(trifluoromethoxy)phenylimino]indolin-2-one (CFMEPI) ionophore. The sensor exhibits a Nernstian response for Fe 3+ ions over a wide concentration range (1.0 ×10 -2 −1.0×10 -6 M) with a slope of 46.7±0.5 mV per decade. The sensor has a response time of 20s and can be used for at least 3 months without any measurable divergence in potential. It was concluded that the sensor response was pH independent in the range of 4.0-8.61. The sensor has some advantages such as short analysis time, particularly high se- lectivity towards iron (III). The sensor was used successfully for direct determination of Fe 3+ in several synthetic and real samples with satisfactory results. Keywords: Fe 3+ -selective electrode, PVC membrane, All-solid-state, determination of Fe 3+ , potentiometer. INTRODUCTION Iron is commonly distributed in many biological organ- isms at various concentration levels and throughout the environment. [1] With only a few possible exceptions in the bacterial world, there will be no life without iron [2]. Iron is very important especially for biological systems, environment systems and industries. Moreover, iron and its compounds have innumerable significant effects. If the concentration of iron is more than the normal level in the body, it may become a health hazard causing liver and kid- ney damages and iron deficiency, especially in babies leads to anemia. Substances which contain iron are known to be carcinogens [3]. Therefore, it is essential to determine iron ion in biological organisms, environment and various in- dustrial wastes. Several methods such as AAS, ICP-MS have been reported for the determination of iron [4-9]. However, these methods have some disadvantages such as being time consuming as they involve multiple sample ma- nipulations and are too expensive [10]. However, potenti- ometric method has so many advantages such as short analysis time, high selectivity and cost effectiveness. Due to the advantages of ion selective electrodes, numerous **Address correspondence to these authors at the Okan University, Voca- tional School of Health Services, Perfusion Techniques, 34959, Istanbul, Turkey; Tel: +216 677 1630; E-mail: ersin.demir@okan.edu.tr; **Pharmaceutical and Medicinal Chemistry Department, Pharmaceutical and Drug Industries Research Division, National Research Centre, Dokki, Cairo 12311, Egypt; Tel: +201003678948; Fax: +202 33370931; E-mail: haboulenein@yahoo.com studies had been reported for the analysis of several heavy metals such Ni 2+ , Co 2+ , Cd 2+ , Hg 2+ [11-16]. However, for determination of Fe 3+ ions in chemical, bio- logical and environmental samples, novel iron-selective sen- sors are urgently needed but there have been merely limited reports of iron-selective sensor in the literature [17, 18]. Only few studies using solid-state ISEs for the determination of Fe +3 were reported in the past [1, 19-23]. But most of the studies for Fe 3+ ion selective electrodes were less selective, working within less range of pH and their stability was not good. In this study, we report the construction of a novel Fe 3+ ion using 5-chloro-3-[4-(trifluoromethoxy)phenylimino] indolin-2-one (CFMEPI) ionophore. This a novel Fe +3 ion selective sensors possessing a wide concentration range, short response time, wide range of pH, and highly selectiv- ity. Furthermore, the proposed sensor could directly measure Fe 3+ in the presence of Fe 2+ ions. EXPERIMENTAL Reagents and Apparatus Tetrahydrofuran (THF), polyvinylchloride (PVC), dioc- tylsebacate (DOS), potassium tetrakis(p-choro) fenylborate (KTClPB) and sodium tetrapenylborate (NaTPB) were pur- chased from Fluka (Bucks, Switzerland). Epoxy (macroplast Su 2227), Hardener (desmodur RFE) and other salts were obtained from Henkel (Germany), Bayer Ag (Germany) and Merck (Darmstad, Germany), respectively. The ionophore 1875-6727/15 $58.00+.00 © 2015 Bentham Science Publishers