Construction and performance characteristics of polymeric membrane electrode and coated graphite electrode for the selective determination of Fe3 + ion

• Three novel Schiff bases (L1, L2 and L3) containing thiazole moiety were synthesized.
• Schiff bases were used for the construction of PME & CGE for the determination of Fe3 +.
• CGE is found to be better with respect to PME.
• The CGE can be used for selective determination of Fe3 + at near nano-level.
• Both the PME and CGE were used to determine Fe3 + in various samples.

Novel Fe3 + ion-selective polymeric membrane electrodes (PMEs) were prepared using three different ionophores N-(4-(dimethylamino)benzylidene)thiazol-2-amine [L1], 5-((3-methylthiophene-2yl) methyleneamino)-1,3,4-thiadiazole-2-thiol [L2] and N-((3-methylthiophene-2yl)methylene)thiazol-2-amine [L3] and their potentiometric characteristics were discussed. Effect of various plasticizers and anion excluders was also studied in detail and improved performance was observed. The best performance was obtained for the membrane electrode having a composition of L2:PVC:o-NPOE:NaTPB as 3:38.5:56:2.5 (w/w; mg). A coated graphite electrode (CGE) was also prepared with the same composition and compared. CGE is found to perform better as it shows a wider working concentration range of 8.3 × 10− 8–1.0 × 10− 1 mol L− 1, a lower detection limit of 2.3 × 10− 8 mol L− 1, and a near Nernstian slope of 19.5 ± 0.4 mV decade− 1 of activity with a response time of 10 s. The CGE shows a shelf life of 6 weeks and in view of high selectivity, it can be used to quantify Fe3 + ion in water, soil, vegetable and medicinal plants. It can also be used as an indicator electrode in potentiometric titration of EDTA with Fe3 + ion.