A new Zn2+-selective sensor based on 5,10,15,20-tetraphenyl-21H,23H-porphine in PVC matrix

PVC based membrane incorporating 5,10,15,20-tetraphenyl-21H,23H-porphine (I ) as an electroactive material, sodium tetraphenyl berate (NaTPB) as an add itive and tri-n-butyl phosphate (TBP) as solvent mediator, in the ratio 200 : 5 : 2 : 150 : (w/w) (PVC : I : NaTPB : TBP) has been used as a Zn2+-sele ctive sensor. The sensor works in a wide concentration range (6.2 x 10(-6_) 1.0 X 10(-1) M) with Nernstian slope (29.0 +/- 1.0 mV/decade of activity) a nd a response time as fast as 12 s. The working pH range of the sensor is 3 .8-7.7 and it can tolerate a nonaqueous content up to 25 % (v/v) (acetone. methyl alcohol and ethyl alcohol). The life time of this sensor is more tha n six months. It exhibits moderate selectivity over a number of cations and has been used as an indicator electrode in the potentiometric titration of Zn2+ against EDTA solution.