Electrochimica Acta 52 (2006) 951–957 Anion recognition using newly synthesized hydrogen bonding diamide receptors: PVC based sensors for carbonate A.K. Jain, V.K. Gupta ∗ , J.R. Raisoni Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667, India Received 4 April 2006; received in revised form 17 June 2006; accepted 26 June 2006 Available online 14 August 2006 Abstract Novel hydrogen bonding diamide receptors viz., N,N I -bis(phenyl)iso phthalohydrazide (I) and N,N I -bis(2,4-dinitrophenyl)isophthalohydrazide (II), have been synthesized and characterized by IR, 1 H NMR and elemental analysis. Spectroscopic investigations indicate high affinity of these receptors for carbonate ion. Polyvinyl chloride (PVC) based membranes of (I) and (II) using tridodecylmethylammonium chloride (TDDMACl) as cation discriminator and diethylphthalate (DEP), dioctylphthalate (DOP), 1-chloronapthalene (CN), tris(2-ethylhexyl)phosphate (TEHP) and bis(2-ethylhexyl)sebacate (DOS) as plasticizing solvent mediators were prepared and investigated as CO 3 2- selective sensors. The best performance was shown by the membrane of composition (w/w) of (II) (4%):PVC (33%):CN (60%):TDDMACl (3%). This sensor works well over a wide concentration range 1.3 × 10 -7 to 1.0 × 10 -3 M with Nernstian compliance (29.0 mV decade -1 of activity) at pH 8.6 with a fast response time of ∼7 s and showed good selectivity for carbonate over a number of anions. The sensor exhibits adequate shelf life (two and half months) with good reproducibility (S.D. ± 0.3 mV) and could be used successfully for the determination of total inorganic carbon in water samples. © 2006 Elsevier Ltd. All rights reserved. Keywords: Amide receptor; Carbonate selective sensor; Total inorganic carbon 1. Introduction Carbonate compounds are used extensively in the manufac- turing of glass, paper, rayon, soaps, detergents and for dying processes in textile industries. Effluents produced from these industries often contain substantial concentration of carbonates. Carbonate is only slightly toxic, but large doses are corrosive to the gastro-intestinal tract where symptoms may include severe abdominal pain, vomiting, diarrhea, collapse and death [1]. Acquaintance of carbonate concentration in blood permits an approximation of the acid–base balance and aids in elucidating abnormal conditions. In view of its widespread occurrence in physiological, industrial and environmental samples, the accu- rate and rapid determination of carbonate is important. Thus, a number of methods such as fourier transform infrared spec- troscopy [2], passive acoustic emission [3], gas chromatography [4] and acoustic wave impedance sensor [5] have been devel- oped for the quantification of carbonate. However, maintenance ∗ Corresponding author. Tel.: +91 1332 285801; fax: +91 1332 273560. E-mail address: vinodfcy@yahoo.com (V.K. Gupta). and operational cost of these techniques are high and require adequate expertise. Therefore, the analysis is mostly limited to laboratory level only. A reliable, low cost, quick and portable analytical technique is the need of the day, especially for the analysis of large number of samples in the field and such require- ments are greatly met with ion sensors. Herman and Rechnitz reported first carbonate selective sen- sors based on tri-fluoroacetyl-p-butylbenzene derivatives [6,7]. However, the applicability of these sensors has often been lim- ited because of their higher selectivities toward other lipophilic anions such as salicylate, perchlorate and thiocyanate. Later on, Scott et al. employed an anion-binding complexone such as mercuric EDTA in the buffer solution to decrease salicy- late interference on the carbonate responsive membrane [8]. The change of cationic site (e.g., tridodecylmethylammonium chlo- ride (TDDMACl)) concentrations in the trifluoroacetophenone (TFA) based membranes was examined by Sokalski et al. to improve their carbonate selectivity [9]. Asymmetric membrane technology was utilized to prevent salicylate from responding to carbonate sensitive membranes in serum carbon dioxide mea- surements [10–12]. Several attempts were also made to increase the selectivity of sensors by incorporating acceptor substituents 0013-4686/$ – see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2006.06.037