Protoporphyrin IX dimethyl ester as active material in PVC matrix membranes for the fabrication of zinc(II) selective sensor

PVC based membrane containing dimethyl-8,13-divinyl-3,7,12,17-tetramethyl-21H, 23H-porphine-2,18-dipropionate (Protoporphyrin IX dimethyl ester (I)) as active material along with sodium tetraphenyl borate (NaTPB) as anion excluder, and dioctyl phthalate (DOP) as solvent mediator in the ratio 15:100:2:200 (w/w) (I:DOP:NaTPB:PVC) exhibited a working concentration range of 1.5×10−5 to 1.0×10−1 M, with the slope of 29.0±1.0 mV/decade of activity and a fast response time (10 s). The working pH range of the sensor is 2.1–4.0 and it could be successfully used in partially non-aqueous medium (up to 40% v/v). The sensor has a life time of more than 5 months. It exhibits good selectivity over a number of cations and has been used as an indicator electrode for the end point determination in the potentiometric titration of Zn2+ against EDTA.