PVC based selective sensors for Ni2+ions using carboxylated and methylated porphine

Abstract

Poly vinylchloride (PVC) based membranes of 4,4′,4″,4‴- 21H,23H-porphine-5,10,15,20 -tetrayl) tetrakis (benzoic acid) (TBAP) and 2,3,7,8,12,13,17,18-octamethyl - 21H, 23H-porphine (OMP) were prepared using dibutyl phthalate (DBP), dioctylphthalate (DOP), dibutyl(butyl)phosphonate (DBBP) and 1-chloronaphthalene (CN) as plastcizing solvent mediators and sodium tetraphenylborate (NaTPB) as an anion excluder for Ni2+ selective sensors. TBAP based membrane exhibits linearity over a wide concentration range 2.0×10-6-1.0×10-1M (0.12 - 5.8×10 3ppm) with a slope of 29.6 mV/decade of activity while OMP based membrane showed linear potential response in the concentration range 1.0×10-5 -1.0× 10-1M (0.60 - 5.8×10 3ppm) with a Nernstian slope of 29.0 mV/decade of activity. The electrode assembly works between pH 2.0 - 7.0, exhibits a fast response time of 10-15s and performed satisfactorily over a period of six months with good reproducibility. Excellent selectivity of the order of 10-3 over a number of cations and quantitative determination of Ni2+ in effluents discharged from electroplating industry demonstrates the utility of the proposed sensor. The electrode assembly was also used as an indicator electrode in the potentiometric titration of Ni2+ with EDTA. © 2003 by MDPI.