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Abstract: Highly selective and sensitive poly(vinyl chloride) (PVC) membrane electrodes based on 6-methyl-4-{[1-(2-thienyl)methylidene]amino}3-thioxo-3,4-dihydro-1,2,4-triazin-5-(2H)-one (MATDTO) as new carriers for gadolinium ion-selective electrode was reported. The membrane solutions containing PVC, o-nitrophenyl octyl ether (NPOE) as plasticizer, sodium tetraphenyl borate (NaTPB) as lipophilic ionic additive, and MATDTO, displays a calibration response for Gd3+ ions over a wide concentration range of 1.0×10−6–1.0×10−1 M with Nernstian slopes of 19.8±0.2mV per decade and a detection limit as 5.8×10−7 M. The sensor has a relatively fast response time of <10s and can be used in the pH range 3.2–8.7 for at least 2 months without any significant divergence in potentials. The selectivity coefficients for mono-, di-, and trivalent cations indicate good selectivity for Gd(III) ions over a large number of interfering cations. The membrane sensor was used as an indicator electrode in the potentiometric titration of Gd(III) ions with EDTA. The proposed electrode was also applied to the determination of concentration of Gd(III) ions in soil and sediment samples and validation with CRMs. [Copyright &y& Elsevier]

Abstract: A highly selective membrane electrode based on nickel(II)-1,4,8,11,15,18,22,25-octabutoxyphthalocyanine (NOBP) is presented. The proposed electrode shows very good selectivity for thiocyanate ions over a wide variety of common inorganic and organic anions. The sensor displays a near Nernstian slope of −58.7±0.6mV per decade. The working concentration range of the electrode is 1.0×10−6 to −1.0×10−1 M with a detection limit of 5.7×10−7 M (33.06ng/mL). The response time of the sensor in whole concentration ranges is very short (<10s). The response of the sensor is independent on the pH range of 4.3–9.8. The best performance was obtained with a membrane composition of 30% PVC, 65% dibutyl phthalate, 3% NOBP and 2% hexadecyltrimethylammonium bromide. It was successfully applied to direct determination of thiocyanate in biological samples, and as an indicator electrode for titration of thiocyanate ions with AgNO3 solution. [Copyright &y& Elsevier]