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 (S-1) and (2-(indol-3-yl) vinyl)-1,3,4-thiadiazole-2-thiol (S-2) 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 (S-2: 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 x 10(-8) mol L-1), near Nernstian slope (29.8 +/- 0.4 mV decade(-1) of activity), wide working concentration range (6.4 x 10(-8)-1.0 x 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 potentimetric 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 S-2 is used as chemosensor for the selective determination of Cu2+ ion. (C) 2013 Elsevier B.V. All rights reserved.