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A new polyvinylchloride-based membrane of rubeanic acid as an ion carrier was fabricated using oleic acid as lipophilic additive. The best performance was exhibited by the membrane having composition rubeanic acid:PVC:OA:o-NPOE as 5:180:18:208 (w/w). The sensor exhibited a Nernstian response for La3+ over a wide concentration range of 3.2 × 10−8 to 1.0 × 10−2 M with a detection limit of 2.5 × 10−8 M. It showed response time of less than 15 s and could be used for 5 months without any significant divergence. The proposed membrane sensor revealed good selectivity for La3+ over a wide variety of other metal ions and can be used in a pH range of 3.5–9.5 and in mixtures containing up to 30% (v/v) non-aqueous content. It was successfully used as an indicator electrode in the potentiometric titration of La(III) against EDTA.

Poly(vinyl chloride) (PVC) based membranes of 5,10,15,20-tetraphenylporphyrinatocobalt, ( I ), incorporating dibutyl phthalate (DBP) in the composition 9:55:36 ( I :PVC:DBP) responds to molybdate (MoO 2− 4 ) over the concentration range 7.6×10 −6 –1.0×10 −1 mol l −1 , pH between 4.9 and 11.3, with a Nernstian slope and a fast response time of 15 s. The membrane shows excellent selectivity towards MoO 2− 4 ions over a number of other anions and exhibits stable response for more than four months. The sensor can be used in non-aqueous medium with no significant change in the value of slope or working concentration range for the estimation of MoO 2− 4 in solutions having upto 25% (v/v) non-aqueous fraction. It was applied for the estimation of molybdenum as molybdate in a sample of molybdenite, a low grade ore.

5,10,15,20-tetraphenylporphyrin (TPP) and 5,10,15,20-tetra(4-methylphenyl) porphyrin (TMPP) have been explored as electroactive materials for preparing poly(vinyl chloride) (PVC) based membrane sensors selective to Ni 2+ . The membrane incorporating TMPP, sodium tetraphenylborate and a solvent mediator (dibutylphthalate) in PVC in the ratio (7 : 35 : 4 : 54) gave the best results, exhibiting Nernstian response in the concentration range 5.6× 10 −6 –1.0×10 −1 mol/l between pH 2.5–7.4 and a fast response time of 20 s. The electrode shows moderate selectivity and has been used for the quantitative determination of Ni 2+ in chocolates and also as an indicator electrode for the end point detection in the potentiometric titration of Ni 2+ against EDTA.

Plasticized membranes using 1-phenyl-3-(2-thiazolyl)-2-thiourea (PTT) and 1-phenyl-3-(2-thiazolyl)-2-urea (PTU) have been prepared and explored as ytterbium ion-selective sensors. Effect of various plasticizers, viz. chloronaphthalene (CN), o-nitrophenyloctyl ether (o-NPOE), dibutylphthalate (DBP), dioctylsebacate (DOS) and anion excluders, sodium tetraphenylborate (NaTPB) and oleic acid (OA) was studied and improved membrane performance was observed. Optimum performance was noted with membrane of PTT having composition of PTT (3.5):PVC (80):DOS (160):NaTPB (1.5) in mg. The sensor works satisfactorily in the concentration range 1.2x10(-7) to 1.0x10(-2) M (detection limit 5.5x10(-8) M) with a Nernstian slope of 19.7 mV decade(-1) of activity. Wide pH range (3.0-8.0), fast response time (10 s), non-aqueous tolerance (up to 20%) and adequate shelf life (12 weeks) indicate the vital utility of the proposed sensor. The proposed electrode comparatively shows good selectivity for Yb3+ ion with respect to alkali, alkaline earth, transition and rare earth metals ions and can be used for its determination in binary mixtures and sulfite determination in white and red wine samples.

Plasticized membranes using 3-(2-pyridinyl)-2H-pyrido[1,2,-a]-1,3,5-triazine-2,4(3H)-dithione (L1) and acetoacetanilide (L2) have been prepared and explored as Cu2+-selective sensors. Effect of various plasticizers, viz. chloronaphthalene (CN), benzyl acetate (BA), o-nitrophenyloctyl ether (o-NPOE), and anion excluders, sodium tetraphenylborate (NaTPB) and oleic acid (OA) was studied in detail and improved performance was observed at several instances. Optimum performance was observed with dithione derivative (L1) having a membrane composition of L1 (5):PVC (120):o-NPOE (240):OA (10). The sensor works satisfactorily in the concentration range 5.0 x 10(-8) to 1.0 x 10(-2) M (detection limit 4.0 x 10(-8) M) with a Nernstian slope of 29.5 mV decade(-1) of activity. Wide pH range (3.0-9.5), fast response time (12s), non-aqueous tolerance (up to 20%) and adequate shelf life (4 months) indicate the vital utility of the proposed sensor. The potentiometric selectivity coefficient values as determined by match potential method (MPM) indicate good response for Cu2+ in presence of interfering ions. The proposed electrode comparatively shows good selectivity with respect to alkali, alkaline earth, transition and some rare earth metals ions. The electrode was used for the determination of copper in different milk powder, water samples and as indicator electrode in potentiometric titration of copper ion with EDTA.