Electroanalytical and naked eye determination of Cu2 + ion in various environmental samples using 5-amino-1,3,4-thiadiazole-2-thiol based Schiff bases

Novel polydentate Schiff bases 4-(5-mercapto-1,3,4-thiadiazol-2-ylimino)pentan-2-one (S1) and (2-(indol-3-yl)vinyl)-1,3,4-thiadiazole-2-thiol (S2) were synthesized and explored as Cu2 + selective polymeric membrane electrodes (PME) using different plasticizers and anionic excluders. The potentiometric data revealed that the PME having the membrane composition (S2: NaTPB: TBP: PVC as 4: 2: 58: 36 (w/w; mg)) is shown to have good results. Thus the coated graphite electrode (CGE) with the same composition as the best PME was also fabricated and investigated as Cu2 + selective electrode. It was found that CGE showed better response characteristics than PME with respect to low detection limit (1.2 × 10− 8 mol L− 1), near Nernstian slope (29.8 ± 0.4 mV decade− 1 of activity), wide working concentration range (6.4 × 10− 8–1.0 × 10− 1 mol L− 1), long shelf life (90 days) and fast response time (9 s). The CGE was used successfully as an indicator electrode for the potentiometric determination of Cu2 + ion against EDTA and also used to quantify Cu2 + ion in soil, water, medicinal plants, vegetables and edible oil samples. The Schiff base S2 is used as chemosensor for the selective determination of Cu2 + ion.