Study On Ion-selective Electrode Based On Schiff Bases And Their Complex As Ionophore

Ion-selective electrode is a kind of chemical sensors which is developed in the modern. It is widely applied in in the water analysis, the biomedicine and the clinical chemical examination, chemical and the mining and metallurgy geology department because of its wide linearity range, the rapid response, the few sample needed, the simple instrument needed, the simple handled, and so on. From valinomycin to supramolecular chemistry of calixarene, or, from the quaternary ammonium salt to the bionic anion carrier, the development direction of ion selective electrode is always the update of inonphore, the optimum of electrode response performance, constantly. In recent years, some schiff bases and schiff base metal complexes accelerate the development of the ion-selective electrode because of the special planar structure and the suitable Louise acidity. This article introduced briefly the development process of the ion-selective electrode, and emphatically in the design, the synthesis of the new schiff base and schiff base metal complexes which is used to PVC polymericn membrane ion selective electrode as ionophore.1.Study on highly selective thiocyanate electrode based on bis-bebzion schiff base binuclear copper(â…¡) complex as neutral carrierIn this study, N, N'- bis[benzoin-(2-aminoethyl)}ethylenediamide binuclear copper compound [Cu(â…¡)-BBAE] and (2-aminoethyl) ethylenediamide binuclear copper compound [Cu(â…¡)- AEED] were synthesized, and they were used as neutral carriers to prepare PVC membrane ion-selective electrode. Based on the orthogonal experiments, the compositions of membrane were optimized because of the effect of membrane composition on electrode's potentiometric response characteristics. The electrode exhibited the best potentiometric response characteristics when the composition of membrane is 5.0 wt.% [Cu(â…¡)- BBAE], 65.0 wt.% plasticizer o-NPOE, 30.0 wt.% PVC. The electrode displayed an anti-Hofmeister selectivity sequence for a series of anions in the following order: SCN^-> C1O₄^- > Sal^- > I^-> NO₃^-> Br^- > Cl^- > NO₂^- > SO₃^2- > F^- > H₂PO₄^- > SO₄^2-. The electrode exhibits near-Nernst response for SCN^- with a slope of 59.0 mV/decade over a wide concentration range 8.5×10^-7-6.8×10^-1 mol/L and a detection limit 5.0×l^-7 mol/L in pH 5.0 phosphate buffer solution at 25℃. AC impedance is used to investigate the response mechanism to thiocyanate of the membrane doped with [Cu(â…¡)- BBAE].2.Study on a new Ce³⁺ ion-selsective electrode based on bis (2-acetyl pyridine)butane-2,3-dihydrzone In this study, bis (2-acetyl pyridine) butane-2, 3-dihydrzone [BAPB] was synthesized, the existence of donor electrom atom N can enhance the integrate ability of ionophore for transition metal and heavy metal ions. The experiment result showed that the electrode had good response characteristics when the membrane composition is 4.9 wt.% [BAPB], 64.1 wt.% plasticizerο-NPOE, 31.0 wt.% PVC, and the internal filling solution is 1.0 mol/L KNO₃ and 1.0×10^-3 mol/L Ce(NO₃)₃. It exhibited Nernstain response with the slope of 19.3 mV/dec within wide concentration of 3.2×10^-6 to 1.0×10^-2 mol/L with a detection limit 2.1×10^-6 mol/L, the pH rang is 2.0 - 5.7. Response time is about 1 minute. The standard deviation of ten replicate measurements was less than±1.0 mV. In addition, the selectivity coefficient which was measured with the separate solution method was compared with the reported Ce³⁺ ion-selective electrode, the result shown that the proposed electrode has good selectivity for Ce(â…¢) ion. Finally, alternating current impedance and equivalent circuit are used to investigate response mechanism, the results indicated that Ce³⁺ transfer from water to membrane, the transfer process was controlled by diffusion. 3. Study on Ce³⁺ ion-selsective electrode based on 2, 6-diaminopyridine macrocyclic schiff base as carrierIn this study, new 2, 6-diaminopyridine macrocyclic schiff base was synthesized, the existence of peculiar macrocyclic and donor electron atoms O, N can enhance the sensitivity and selectivity for metal ions so as to construct a Ce³⁺ ion-selective electrode with good response characteristics. The experiment result shown that the electrode had good response characteristics when the membrane composition is 4.6 wt.% ionophore, 62.7 wt.% plasticizer o-NPOE, 31.7 wt:% PVC, 1wt% ion-additive NaTPB. It exhibited Nernstain response with the slope of 19.0 mV/dec within wide concentration of 1.0×10^-5 to 1.0×10^-2 mol/L with a detection limit 5.0×10^-6 mol/L, the best pH is 3.0. The standard deviation (SD) of the electrode potential reading over a period of 8 h in 1.0×10^-2 mol/L Ce(NO₃)₃ solution (pH 3.0) is 2.3 mV (n=45), and the same electrode dipped alternatively into solutions of 1.0×10^-3 mol/L and 1.0×10^-2 mol/L Ce(NO₃)₃ solution is 1.1 mV over 2 h (n=12), response time is about 40 seconds. In addition, the selectivity coefficient which was measured with the separate solution method was compared with the reported Ce³⁺ ion-selective electrode, the result showed that the proposed electrode has good selectivity for Ce(â…¢) ion. Finally, the electrode was applied to the direct determination of cerium in water samples, the result indicated the Ce³⁺ ion-selective electrode can be used to the Ce³⁺ detection in samples.