Crown ether-dendrimer based potentiometric Na + sensor electrode B. Sethi a,⇑ , S. Chandra b , S. Kumar a , R. Singh c , L.P. Singh d a Department of Chemistry, M.K.P. (P.G.) College, Dehradun, Uttarakhand, India b Department of Metallurgical Engineering and Material Science, Indian Institute of Technology, Mumbai, India c Department of Chemistry, D.B.S Degree College, Dehradun, Uttarakhand, India d Central Building Research Institute, Roorkee, Uttarakhand, India article info Article history: Received 30 July 2010 Received in revised form 15 November 2010 Accepted 17 November 2010 Available online 25 November 2010 Keywords: Carbosilane dendrimer Sodium-selective electrode Sensors PVC membrane Potentiometry abstract Poly(vinyl chloride) (PVC)-based membranes of silacrown end grafted carbosilane dendrimer (I) with sodium tetraphenylborate (NaTPB) as an anion inhibitor and dibutylphthalate (DBP), dioctylphthalate (DOP), dibutyl (butyl) phosphonate (DBBP) and 1-chloronaphthalene (CN) as plasticizing solvent media- tors were prepared and used as Na + -selective electrodes. Optimum performance was observed with the membrane having I–PVC–NaTPB–DOP in the ratio 1:33:1:65 (w/w). The electrode works well over a wide concentration range 1.5  10 6 –1.0  10 1 M with Nernstian compliance 56.0 mV/decade between pH 5.8 and 9.2 with a fast response time of about 15 s. The selectivity relative to alkali, alkaline earth and transition heavy metal ions is good. The selectivity coefficient values towards potassium ions have been calculated to be 2.3  10 4 by utilizing Fixed Interference Method. The proposed electrode could be used for at least 2 months without considerable alteration in its potential. The effect of nonionic surfactants Tween 20, Tween 80, Triton X 100, Span 20 and Span 60 on the potentiometric properties of the sodium selective membrane was also studied. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction Dendrimers are perfect and unified macromolecules with regu- lar and highly branched architectures that are obtained from a repetitive procedure [1]. Due to their distinctive chemical and physical properties, they find applications for many fields in mate- rial science [2]. The end-functionalized dendritic macromolecules with specific groups were studied by many researchers who used the electro-active groups or molecular recognition groups that could find applications as components in sensors, electro-devices, etc. [3]. The crown ether end-capped dendrimers form one such class of end-functionalized dendritic macromolecules and were used as the ion selective sensor [4]. Analytical methods for deter- mining the alkali metal ions have been extensively studied due to the importance of sodium and potassium in biological processes. Sodium forms a major cation of extracellular fluid. The typical daily diet contains 130–280 mmol (8–15 g) sodium chloride. The body requirement is for 1–2 mmol per day, so the excess is excreted by the kidneys in the urine. Hyponatraemia (lowered plasma [Na + ]) and hypernatraemia (raised plasma [Na + ]) are associated with a variety of diseases and illnesses in the body and thus the accurate measurement of [Na + ] in body fluids is of great impor- tance. Recently there has been increasing interest in the develop- ment of neutral carrier-based sodium ion-selective electrodes as alternatives of sodium ion-selective glass electrode which suffered from certain difficulties in clinical use. The dynamic response gen- erated in ISE’s is mainly by selective complexation of the target ion by ionophores dispersed in a poly(vinyl chloride) (PVC) matrix. These ISEs provide one of the most powerful sensing methods be- cause it is possible to select various sensory elements according to the charge and size of the target ion in clinical and environmental assays [5–12]. Based on the recent developments in host–guest chemistry, polymeric membrane ISE’s for sodium ion have been extensively developed by the use of crown ethers and related mac- rocyclic hosts as well as acyclic ligands [13–17]. Many of these ISEs exhibit excellent selectivity for sodium ion as a guest and are now commercially available [18–20]. The present paper deals with sila- crown end grafted carbosilane dendrimer [I] (Fig. 1) based ISE for selective determination of sodium ions. 2. Experimental 2.1. Reagents and apparatus All reagents used were of analytical reagent grade and were used without further purification. High molecular weight poly(vi- nyl chloride) (PVC) was obtained from Aldrich, USA; sodium tetra- 1572-6657/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jelechem.2010.11.025 ⇑ Corresponding author. Tel.: +91 135 2654829; fax: +91 135 2748677. E-mail address: bsethi.30@gmail.com (B. Sethi). Journal of Electroanalytical Chemistry 651 (2011) 185–190 Contents lists available at ScienceDirect Journal of Electroanalytical Chemistry journal homepage: www.elsevier.com/locate/jelechem