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-methylphenyl) porphyrin (TMPP) have been explored as electroactive materials for preparing poly(vinyl chloride) (PVC) based membrane sensors selective to Ni2+. 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 Ni2+ in chocolates and also as an indicator electrode for the end point detection in the potentiometric titration of Ni2+ against EDTA.