Study On Synthesis Of Schiff Bases And Their Complex And Application In Electroanalysis Chemistry

Ion-selective electrodes (ISEs) constructed by incorporating ion carriers into solvent polymetric membranes have been widely applied for the direct determination of several ionic species. Many of them showed potentiometric anion-selectivity sequences which differed from the Hofmeister pattern. The key components of the sensors are lipophilic complexing agents capable of reversibly binding ions. This thesis focuses on design and synthesis of several novel compounds and basic studies on solvent polymeric membrane ion-selective electrodes containing the compounds. The electrodes can be successfully applied to practice sample analysis. Recently, organic-complex has drawn much attention because of their attractive advantages such as simple and economical preparation, predetermined selectivity and good recognition properties. In this thesis, a chemical sensor based on novel Schiff base and their complex has been described, which provides the possibility and basis of using the novel sensor for determination of the Schiffbase and their complex. Partâ… of the thesis deals with design of some novel carriers for poly (vinyl chloride) (PVC) membrane ion-electrode with high selectivity to five kinds of Schiff base and their organic-metal complex respectively.Partâ… Studies on Schiff's application on mercury (â…¡)ion selective electrode1. In this study, a new poly (vinyl chloride) (PVC) membrane ion-selective electrode for Hg²⁺ ion based on bis-salicyladehyde-diaminjodipropylamine(BSDDA) as a neutral ion carrier was prepared. This electrode exhibited good selectivity toward Hg²⁺ ion over a wide variety of other metal ions. Effects of experimental parameters such as membrane composition, nature and amount of plasticizer, the amount of additives were investigated. The electrode exhibited a Nernstian slope of 30.5±0.4 mV per decade of Hg²⁺ ion over a concentration range 9.5x10^-7 to 6.4x10^-2 mol/L of Hg²⁺ ion in the pH range 1.5 to 3.5. The response time was about 10s to 25s and the detection limit was 7.0±0.2×10^-7mol/L. The electrode can be used for More than 2 months with no an apparent divergence in potential. The proposed electrode was used as an indicator electrode in the potentiometric titration of EDTA.2. A new PVC membrane electrode based on bifuranaldehyde- thiocarbazone (BFATC) that is highly selective to Hg(â…¡) ions is studied successfully. The electrode shows excellent potentioMetric response characterstics and presented a Nerstian response for mercury ions over a wide concentration range from (1.0×10^-6 to1.0×10^-2 mol/L) with detection limit of 8.0×10^-7mol/L and a slope of 29.7 mV per decade. It has a response time of<20 s and can be used for at least 3 months without any apparent divergence in potential. The electrode can be used in the pH range from 2.0 to 5.0. The proposed electrode exhibited quiet good discriminating ability toward Hg²⁺ ion in comparison with various metal ions. The sensor was also applied to an indicator electrode for potentiometric titration of Hg²⁺ ions with I^- and in the determination of Hg²⁺ in some water samples.3. A new PVC membrane mercury(â…¡) ion electrode based on N,N-dime-thyl-formamide-salicylacylhydrazone (DMFAS) as an ionophore is described, which shows excellent potentiometric response characteristics and displays a linear log[Hg²⁺] versus EMF response over a wide concentration range between 6.2×10^-7 and 8.0×10^-2 mol/L with a Nerstian slope of 29.6mV per decade and a detection limit of 5.0×10^-7 mol/L. The response time for the electrode is less than 30 s and the electrode can be used for more than 2 months with less than a 2 mV observed divergence in a potentials. The proposed electrode exhibits very good selectivity for mercury (â…¡) ions over many cations in a wide pH range (pH 1-4). The electrode was also applied to the determination of a mercury (â…¡) ion in vegetables and in Azolla filiculoides.Partâ…¡Studies on Schiff complex's application on thiocyanate ion selective electrodeThe utilization of a newly synthesized Cu (â…¡) complex, (salicaldehydeoctamine-Cu (â…¡) complex), as a novel ionophore for the preparation of anion-selective polymeric membrane electrode was tested. The results show that the electrode based on salicaldehydedioctamine-Cu (â…¡) complex demonstrates excellent potentiometric response towards thiocyanate ion and anti-Hofmeister selectivity sequence in following order: SCN^->ClO4^->Sal^->I^->Br^->NO₂^->NO₃^->SO₃^->Cl^->SO₄^2->H₂PO₄^-. The ionophore presented anti-Hofmeister behavior with enhanced potentiometric delectivity toward thiocyanate ion compared to other anions. The influence of some experimental parameters such as membrane composition, and concentration of internal solution on the potential response of the SCN^- sensor were investigated. The electrode exhibits a near Nernstian response for SCN^- over a wide concentration range (1.0×10^-1 to 3.0×10^-6mol/L) with a slope -55.7 mV per decade and a detection limit of 1.0×10^-6mol/L in a pH range of 5, It have a fast response time of about 15 s. The response mechanism is discussed in view of the AC impedance technique and the UV spectroscopy technique. The electrode exhibits the advantages of high selectivity, low detection limit, reproducibility and simplicity. The electrode was successfully applied to the determination of thiocyanate ion in waste water and human saliva.Partâ…¢Studies on Schiff complex's application on salicylate ion selective electrodeA new salicylate-selective PVC membrane electrode based on a new Schiff base tetranuclear copper complex of O-Vannlin-methionine [Cu(â…¡)4-TVM] as a neutral carrier is described. As a result, this electrode displays a preferential potentiometric response to salicylate. Such as Gly-Sn(â…£)-SAADB, the electrode exhibits Nernst response with an average slope of 54.8mV/decade over the concentration range from 8.0×10^-6 mol/L to 1.0×10^-1mol/L. The limit of detection is 2.0×10^-6 mol/L. After used TOMAC1 as additive, the electrode exhibits near-Nernstian potential linear range of 1.5×10^-6-1.0×10^-1mol/L with a detection limit of 8.0×10^-7mol/L and a slope of -56.3 mV/decade in pH 3.0-8.0 of phosphorate buffer solution at 20℃. And an anti-Hofmeister selectivity sequence in the following order: Sal^->ClO₄^->SCN^->I^->NO2^->NO₃^->Br^->Cl^->SO₃^2->SO₄^2->H₂PO₄^-. Thanks to the tetranuclear copper (â…¡) in the carrier, the electrode has the advantages of simplicity, fast response, fair stability and reproducibility and low detection limit. The response mechanism to the electrodes is because of the infection caused by complex atomic which link central atomic directly with impedance technique and the UV spectroscopy technique. The electrode can be applied to analyses of medicine and the results obtained are in fair agreement with the results given by a standard method。...