Koteswara Rao Bandi

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 Cu(2+) 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 Cu(2+) selective electrode. It was found that CGE showed better response characteristics than PME with respect to low detection limit (1.2×10(-8)molL(-1)), near Nernstian slope (29.8±0.4mV decade(-1) of activity), wide working concentration range (6.4×10(-8)-1.0×10(-1)molL(-1)), long shelf life (90days) and fast response time (9s). The CGE was used successfully as an indicator electrode for the potentiometric determination of Cu(2+) ion against EDTA and also used to quantify Cu(2+) ion in soil, water, medicinal plants, vegetables and edible oil samples. The Schiff base S2 is used as chemosensor for the selective determination of Cu(2+) ion.

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

Novel Fe(3+) 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)molL(-1), a lower detection limit of 2.3×10(-8)molL(-1), and a near Nernstian slope of 19.5 ± 0.4 mVdecade(-1) of activity with a response time of 10s. The CGE shows a shelf life of 6 weeks and in view of high selectivity, it can be used to quantify Fe(3+) ion in water, soil, vegetable and medicinal plants. It can also be used as an indicator electrode in potentiometric titration of EDTA with Fe(3+) ion.

Fabrication of coated graphite electrode for the selective determination of europium (III) ions

Preliminary complexation study showed that two ligands (ionophores) (2-((2-phenyl-2-(pyridin-2-yl)hydazono)methyl)pyridine) [L1], (2-((2-phenyl-2-(pyridin-2-yl)hydazono) methyl)phenol) [L2] can act as europium selective electrode. Europium selective coated graphite electrodes (CGE) were prepared by using ligands [L1] and [L2] and their potentiometric characteristics were determined. Membranes having different compositions of poly(vinylchloride) (PVC), the different plasticizers, anionic additives and ionophores were coated onto the graphite surface. The potential response measurements showed that the best performance was exhibited by the proposed CGE. This electrode had the widest working concentration range, Nernstian slope and fast response times of 10s. The selectivity studies showed that this electrode have higher selectivity towards Eu(3+) over a large number of cations. Furthermore, the electrode generated constant potentials in the pH range 2.7-9.0. This electrode can be used to quantify europium in soil, binary mixtures and also used as an indicator electrode in the potentiometric titration of Eu(3+) with EDTA. The proposed electrode was also successfully applied to the determination of fluoride ions in real samples.

A comparative study on fabrication of Mn2+ selective polymeric membrane electrode and coated graphite electrode.

Poly(vinyl chloride)-based membranes of two ligands 2,4-bis(2-acetoxybenzylamino)-6-phenyl-1,3,5-triazine (L1) and N2,N4-di(cyanoethyl)-2,4-bis(2-acetoxybenzylamino)-6-phenyl-1,3,5-triazine (L2) were fabricated and explored as Mn(2+) ion selective electrodes. The performance of the polymeric membranes electrodes of ionophores with different plasticizers (dibutylphthalate, benzoic acid, o-nitrophenyloctyl ether, 1-chloronapthalene and tri-n-butylphosphate) and anion excluders (sodium tetraphenylborate and potassium tetrakis p-(chloro phenyl)borate) was looked in to and the better results were obtained with the membrane having composition L2: NaTPB: DBP: PVC as 6: 3: 56: 35 (w/w; mg). The coated graphite electrode (CGE) with same composition was also fabricated and investigated as Mn(2+) selective electrode. It was found that CGE showed better response characteristics than PME. The potentiometric response of CGE was independent of pH in the range 3.0-9.0 exhibiting the Nernstian slope 29.5 ± 0.3 mVdecade(-1) of activity and working concentration range 4.1 × 10(-7)-1.0 × 10(-1)mol L(-1) with a limit of detection 6.7 × 10(-8)mol L(-1). The electrode showed a fast response time of 12s with a shelf life of 105 days. The proposed CGE could be successfully used for the determination of Mn(2+) ions in different water, soil, vegetables and medicinal plants also used as an indicator electrode in potentiometric titration with EDTA.

Nano-level monitoring of Er(III) by fabrication of coated graphite electrode based on newly synthesized Schiff base as neutral carrier

Plasticized membranes using N-(-3-((thiazol-2-ylimino)methyl)benzylidene)thiazol-2-amine (S1) and 5-((-3-((5-mercapto-1,3,4-thiadiazol-2-ylimino)methyl)benzylidene)amino)-1,3,4-thiadiazole-2-thiol (S2) have been prepared and explored as Er (III) selective electrodes. Effect of various plasticizers viz. dibutylphthalate, tri-n-butylphosphate, dioctylphthalate, acetophenone, 1-chloronapthalene, o-nitrophenyloctylether, and anion excluders viz. sodium tetraphenylborate and potassium tetrakis-p-(chlorophenyl)borate was studied in detail and improved performance was observed. Optimum performance was observed for the membrane electrode having a composition of S2: PVC: o-NPOE: KTpClPB in the ratio of 4: 38: 55: 3 (w/w, mg). The performance of the PME based on S2 was compared with CGE. The electrodes exhibit Nernstian slope for Er (III) ion with detection limit 5.4 × 10(-8)mol L(-1) for PME and 6.1 × 10(-9)mol L(-1) for CGE. The response time for PME and CGE was found to be 12s and 9s respectively. The practical utility of the CGE has been demonstrated by its usage as an indicator electrode in potentiometric titration of EDTA with Er (III) solution and determination of fluoride ions in mouthwash solution. The proposed electrode was also applied to the determination of added Er(3+) ion in water and binary mixtures. It is found that the electrode could be able to recover the Er(3+) ion in 96.2-99.5%.