Anion recognition through novel C-thiophenecalix[4]resorcinarene: PVC based sensor for chromate ions

Novel ionophore, C-thiophenecalix[4]resorcinarene (1) has been synthesized and characterized by IR, NMR and C, H, N analysis. Poly(vinyl chloride) (PVC) based membranes of ionophore (1) using dibutylphthalate (DBP), dioctylphthalate (DOP), 1-chloronapthatene (CN), tris(2-ethylhexyl) phosphate (TEHP) and bis(2-ethylhexyl)sebacate (DOS) as plasticizing solvent mediators were prepared and used as CrO42- selective sensors. Of the various sensors prepared, the one with membrane composition 2:66:120 mg (I: PVC: DBP) exhibited the best performance. This sensor works well over a wide concentration range 5.6 x 10(-6)-1.0 x 10(-1) M (detection limit similar to 0.30 ppm) with Nernstian compliance (29.0 mV per decade) between pH 6.5-10.0 with a fast response time of similar to 13 s. The selectivity coefficient values as determined by fixed interference method (FIM) indicate excellent selectivity for CrO42- ions over a large number of anions. The sensor exhibits adequate shelf-life ( similar to5 months) with good reproducibility (S.D. +/- 0.2 mV). The sensor has been used in the potentiometric titration of chromate with Pb(II). Determination of chromium in electroplating waste using the sensor was successfully achieved. (C) 2004 Elsevier B.V. All rights reserved.