Cobalt (II)-selective coated graphite electrode based on a diamine donor Schiff base ionophore

A PVC membrane coated graphite electrode based on the Schiff base 4,4'-(((3,3'-dimethyl-[1,1'-biphenyl]-4,4'-diyl) bis(azaneylylidene)) bis(methaneylylidene)) diphenol (L) was fabricated. Membrane coated electrode having compositions L(4%): NaTPB(2.5%):NPOE(51%):PVC(42.5%) showed best performance towards Co2+ ions over a wide working concentration range 2.8 x 10-7-1.0x10-1 M with lower detection limit 7.6 x 10-8 mol L-1 and with a fast response time of 15 s. The electrode could be used over a period of 90 days without significant change in its performance characteristics. Interference study of the electrode revealed its high selectivity for Co2+ ion over several interfering ions. The electrode worked well in the pH range of 2.0 to 8.0 and also worked satisfactory in the presence of 20% (v/v) non-aqueous solvents. The electrode was successfully used as indicator electrode in the potentiometric titration of Co2+ against EDTA and also in the quantitative determination of Co2+ ions in various samples.