Anion recognition through modified calixarenes: a highly selective sensor for monohydrogen phosphate

PVC-based membranes of 5,11,17,23,29,35-hexa-tert-butyl-37,38,39,40,41,42-hexakis(carbamoylmethoxy)calix[6]arene (I) as electroactive material with dioctyl phthalate (DOP), 1-chloronaphthalene (CN), dibutyl phthalate (DBP), o-nitrophenyl octyl ether (NPOE) and tris(2-ethylhexyl) phosphate (TEP) as plasticising solvent mediators have been prepared and used for phosphate determination. The membrane having composition PVC:I (150:5.7) exhibited the best result with linear potential response in the concentration range of 1.77 × 10−5 to 1.0 × 10−1 M of HPO42− with a slope of 33.0 mV/decade. The membrane worked satisfactorily in non-aqueous medium up to 5% (v/v) non-aqueous content. The selectivity coefficient values for mono- and divalent anions indicate good selectivity for phosphate over a large number of anions. The proposed sensor has been successfully used in the real sample analysis.