Potentiometric Membrane Electrode for Salicylate Based on an Organotin Complex with a Salicylal Schiff Base of Amino Acid

Application of metalloporphyrin grafted-graphene oxide for the construction of a novel salicylate-selective electrode

Due to the vast applications of salicylate ion, development of a simple and selective procedure for its determination is of practical interest. Herein, the unique properties of graphene oxide are combined with the anion selectivity of metalloporphyrins to construct a novel salicylate selective electrode. This electrode is prepared by incorporating Cu(II)–5-4 (aminophenyl)-10,15,20-triphenyl porphyrin grafted-grapheneoxide (CuTPP-GO) into the plasticized poly (vinyl chloride) membrane. Effects of plasticizer nature, Cu TPP-GO concentration and anionic and cationic additives on the potential response of the electrode are investigated. The electrode with the membrane composition of 25% PVC, 50% NPOE, 5% NaTPB and 20% Cu TPP-GO provided the best behavior. This sensor shows a Nernstian response (57.8 mV.decade-1) in the concentration range of 5.0 × 10-1–5.0 × 10-7M with detection limit of 8.0 × 10-8M. sensor response is stable in the pH range of 5–7 and shows a discriminating ability for salicylate compared to most common anions. The sensor was successfully used for determination of salicylate in an aspirin tablet.

A novel thiocyanate-selective electrode based on a zinc–phthalocyanine complex

A novel thiocyanate (SCN-)-selective PVC membrane electrode based on a zinc-phthalocyanine (ZnPc) complex as neutral carrier is described. The membrane electrode containing ZnPc with 5.1% (w/w) ionophore, 29.2% (w/w) PVC, and 65.7% (w/w) 2-nitrophenyl octyl ether (o-NPOE) as plasticizer displayed an anti-Hofmeister selectivity sequence, SCN- > Sal- > I- > ClO4- > Br- > Cl- > NO3- > NO2- > H2PO4- > SO4(2-)), and exhibited near-Nernstian potential response to thiocyanate ranging from about 1.0 x 10(-1) to 1.0 x 10(-6) mol L(-1) with a detection limit of 7.5 x 10(-7) mol L(-1) and a slope of 58.1+/-0.5 mV per decade in pH 3.0 phosphate buffer solution at 25 degrees C. This preferential response is believed to be associated with the unique coordination between the central metal of the carrier and thiocyanate.