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

Novel ionophore, C-thiophenecalix[4]resorcinarene (I) has been synthesized and characterized by IR, NMR and C, H, N analysis. Poly(vinyl chloride) (PVC) based membranes of ionophore (I) using dibutylphthalate (DBP), dioctylphthalate (DOP), 1-chloronapthalene (CN), tris(2-ethylhexyl) phosphate (TEHP) and bis(2-ethylhexyl)sebacate (DOS) as plasticizing solvent mediators were prepared and used as CrO(4)(2-) selective sensors. Of the various sensors prepared, the one with membrane composition 2:66:120mg (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 approximately 0.30ppm) with Nernstian compliance (29.0mV per decade) between pH 6.5-10.0 with a fast response time of approximately 13s. The selectivity coefficient values as determined by fixed interference method (FIM) indicate excellent selectivity for CrO(4)(2-) ions over a large number of anions. The sensor exhibits adequate shelf-life ( approximately 5 months) with good reproducibility (S.D. +/- 0.2mV). 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.