PORPHYRINS AS CARRIER IN PVC BASED MEMBRANE POTENTIOMETRIC SENSORS FOR NICKEL(II)

5,10,15,20-tetraphenylporphyrin (TPP) and 5,10,15,20-tetra(4-methylphe nyl) porphyrin (TMPP) have been explored as electroactive materials fo r preparing poly(vinyl chloride) (PVC) based membrane sensors selectiv e to Ni2+. The membrane incorporating TMPP, sodium tetraphenylborate a nd a solvent mediator (dibutylphthalate) in PVC in the ratio (7:35:4:5 4) gave the best results, exhibiting Nernstian response in the concent ration range 5.6x10(-6)-1.0x10(-1) mol/l between pH 2.5-7.4 and a fast response time of 20 s. The electrode shows moderate selectivity and h as been used for the quantitative determination of Ni2+ in chocolates and also as an indicator electrode for the end point detection in the potentiometric titration of Ni2+ against EDTA. (C) 1997 Elsevier Scien ce B.V.