Talanta 86 (2011) 121–127 Contents lists available at SciVerse ScienceDirect Talanta j ourna l ho me page: www.elsevier.com/locate/talanta Novel monohydrogenphosphate ion-selective polymeric membrane sensor based on phenyl urea substituted calix[4]arene Nishith R. Modi, Bhargav Patel, Manishkumar B. Patel, Shobhana K. Menon ∗ Department of Chemistry, School of Sciences, Gujarat University, Navrangpura, Ahmedabad 380009, Gujarat, India a r t i c l e i n f o Article history: Received 10 June 2011 Received in revised form 23 August 2011 Accepted 24 August 2011 Available online 30 August 2011 Keywords: Phenylurea substituted calix[4]arene Ion selective electrode Monohydrogen phosphate Anion recognition Sensor a b s t r a c t A highly selective and sensitive PVC membrane, containing phenylurea substituted calix[4]arene was found to be a suitable ionophore for monohydrogen phosphate (HPO 4 2- ) ions that exhibited a Nernstian response (with a slope of -29.4 ± 0.3 mV decade -1 ). The working concentration range of the electrode was 6.0 × 10 -8 –1.0 × 10 -1 mol L -1 with a detection limit of 2.0 × 10 -8 mol L -1 . The response time of the sensor in the whole concentration range is very short (<8 s), with a considerable lifetime of at least 15 weeks. The sensor possesses the advantages of short response time, low detection limit and a high selectivity towards a large number of inorganic anions. The developed sensor was used as an indicator electrode in potentiometric titration of monohydrogen phosphate ion with barium chloride. The proposed sensor was successfully applied for the direct determination of monohydrogen phosphate in real life samples. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Supramolecular chemistry of anions has been a field of growing interest during the last few years and there has been a large number of appealing reviews on the chemistry of anion recognition as well as on the development of host receptors for anions [1–3]. The inter- est in ion-selective electrodes has grown over recent years as they are easy-to-use devices that allow rapid and accurate analytical determination of chemical species at relatively low concentrations, with a reasonable selectivity and low cost. The rapid determina- tion of minute quantities of ionic species by simple methods is of special attention in analytical chemistry. Ion selective electrodes based on solvent polymeric membrane incorporating ion carriers have shown to be very useful tools for the analysis of many cations and anions. A great number of ionophores have been developed and found extensive applications in potentiometric sensors for the determina- tion of respective ions in real samples. The macrocyclic compounds, which are excellent ionophores, are being employed as the car- riers in metal selective extraction, phase transfer catalysis and membrane transport as they bind the metal ions selectively [4–7]. Macrocyclic compounds are cyclic, organic molecules containing N, S, O, etc. capable of forming electron rich interior cavities and possess the ability to complex with metal ions of compatible dimensions. Complexation studies between macrocyclic ligands ∗ Corresponding author. Tel.: +91 79 26302286; fax: +91 79 26308545. E-mail address: shobhanamenon07@gmail.com (S.K. Menon). and metals provide valuable information for construction and design of sensors. Calixarenes are fascinating objects for the study of host guest interactions with pronounced binding affinities to var- ious metals. The ease of chemical modification is one of the main attractive features of calixarenes as it enables alterations in the ion-complexing selectivity by simply switching from one ligating functional group to another. The uses of calixarenes as the basis for ion-recognition in cation sensor systems is well established [8–12]. A few calixarene derivatives for anion binding have been reported [13–16]. The significance of monitoring phosphate concentration lev- els spans all areas of science and technology. A system that can continuously and selectively detect phosphates levels in aque- ous solutions will find numerous applications in fields, such as environmental monitoring, biomedical research, clinical chemistry and pharmacology because phosphorus is an essential mineral for the human body and all other living organisms [17–21]. Mea- surement of phosphate levels in environmental water samples is usually achieved using laboratory-based automated flow appara- tus. A number of investigations, into the development of several phosphate-selective electrodes, have been reported in the lit- erature [22–25]. Organotin complexes have been flourishing in the past as phosphate-selective ionophores in PVC-based ISEs [26–28], along with thiourea compounds [29,30], uranyl salophene derivatives [31,32], molybdenum-based compound [24], cyclic polyamine compounds [33,34], modified calix[6]arene deriva- tive [35] and also an organoborane complex [36]. Still many problems like interference of other anions, lower detection limit, lifetime and longer response time have been encountered. 0039-9140/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2011.08.042