Title of Invention

AN IMPROVED ION-SELECTIVE ELECTRODE USEFUL FOR SENSING POTASSIUM ION FLUIDS

Abstract

The present invention provides an improved ion-selective electrode useful for sensing potassium ion in fluids and device thereof which comprises in combination a metallic part , the said metallic part being in direct contact with a metal foil having layer of a thermally stable conducting polymer selected from polyindole, polycarbazole and the said metal foil conducting polymer coated layer being provided with a layer of PVC incorporated neutral ion carrier and the said metal part, polymer coated metal foil and PVC incorporated neutral ion carrier layer being encased in an insulating protective outer covering in such a manner so as to allow fluid contact with the resultant electrode.

Full Text

The Present invention particularly relates to an improved ion-selective electrode use-fill for sensing potassium ion in fluids Ion-selective electrodes (ISEs) have grown at an ever increasing rate due to their need in the various spheres of life particularly in the analytical, biological and clinical areas. Accordingly extensive studies have been made on the development of ion-selective electrodes (ISEs) based on unblocked (with conventional double barrel configuration) and blocked (coated wire electrode, CWE) interfaces. Various extensive investigations on the ISE baaed on unblocked interface have been made with several of them at commercial scale. There are several potassium ion selective electrodes based on conducting polymers are known in art. One type of such electrode was described by A. Cadogen, Z. Gao, A. Lewenstam, A. Ivaska and D. diamond [Anal Chem., 64 (1992) 2496-2501] wherein they construct solid state contact in membrane ion selective electrode. The major drawbacks were- i) noise at the steady-state potential and it) the sharp variation in a random order of the standard electrode potential Another type of such electrode was described by T. Momma, S. Komaba, M. Yamamoto, T. Osaka, and S. Yamauchi, [Sensors and Actuators, 1995, B 24-25, 724-728] wherein they used polypyrrole doped with an cation exchanger and valinomycin impregnated PVC membrane. The major drawback was in the complicated construction of the electrodes using with ion exchanger and random variation in the standard potential of the ion selective electrode. The main object of the present invention is to provide an improved ion-selective electrode useful for Sensing potassium ion in fluids which obviates the drawbacks of the either to known ion-selective electrode for the K+ion. Another objective of the present invention is to provide an improve ISE using as such conducting Polytmer (i.e. without any cation exchanger). Another objective of the present invention is to use conducting polymer such as polvindole and polycarbazole. Yet another objective of the present invention is to provide an ion-selective electrode having layers of conducting polymer and neutral ion carrier mediated Polyvinyl Chloride membrane (PVC). Still another object is to provide a device useful for sensing potassiun ion in fluid incorporating the improve ion-selective electrode of die present invention. An embodiment of the improved ion-selective electrode of the present invention is shown in a schematic diagram in fig. 1 of the drawing accompanying mis specification, the various parts of the said ISE are, less corrosive metal (1), non corrosive insulating material (2), Platinum (3). Accordingly, the present invention provides an improved ion-selective electrode useful for sensing potassium ion in fluids which comprises in combination a metallic part (1), the said metallic part being in direct contact with a metal foil (2) having layer of a thermally stable conducting polymer selected from polyindole, polycarbazole and the said metal foil conducting polymer coated layer being provided with a layer of pvc incorporated neutral ion carrier and the said metal part, polymer coated metal foil and pvc incorporated neutral ion carrier layer being encased in an insulating protective outer covering (3) in such a manner so as to allow fluid contact with the resultant electrode. In an embodiment of the present invention the metallic part used is a non corrosive metal or alloy. In another embodiment of the present invention the metal foil used is selected from Gold, Platinum, Titanium and stainless steel. In yet another embodiment of the present invention the PVC incorporated neutral ion carrier used is selected from Valinonmycin, various crown ethers or its derivatives like dibenzo- 18-crown-6. In still another embodiment of the present invention , a device useful for sensing potassium ion in fluids characterized by incorporation of an improved ion selective electrode in combination with a known reference electrode being placed in suitable container for holding the fluid in which potassium ion is to be detected, the potential outputs of the said electrode pair being connected to means for measuring potential difference which provides die direct measurement of potassium ion concentration. The reference electrode used may be such as Calomel electrode, Ag/AgCl electrode. The means used for measuring the potential difference may be such as Voltmeter, digital display meter, a computer. The improved ISE of the present invention is novel as it uses these conducting pojymers and also without cation exchangers. The designing of the coated wire electrode is the combination of electron conductor and the ionic conductor interface. The interface of the electron conductor and ionic conductor is highly susceptible to various uncontrolled parameters leading to variable electrochemical background Introduction of the electroactive conducting polymer film between the electron conductor and ion conductor is likely to make the interfacial potential least sensitive to these parameters. Additionally introduction of a film with cation exchange capacity between metal and PVC interface may result in the establishment of concentration cell at the both sides of the PVC interface . The conducting polymers used by us do not show any cation exchange behaviour. Therefore, the establishment of concentration cell at only one side of PVC interface is possible. However, The better reproducibility of the standard electrode potential in the present case is possibly attributed to : i) good electroactivity of these polymers ii) high hydrophobisity and iii) better conductivity of The polymer film. Polyindole or polycarbazole was electrochemically polymerised dirough a non-aqueous solution having supporting electrolyte and monomer of The polymer over the electrode, which is shown in Fig.l. After getting a good film me polymer film was washed and dried A neutral ion carrier impregnated PVC membrane was casted over The conducting polymer film through a THF (Tetra hydro&rane) solution having some plastisizer and ion carrier. The potentiometric responses of the ion-sensor constructed above were carried out in Tris-HCl buffer, at various pH and using a double junction calomel electrode with the cell assembly; Calomel electrode/ KCl (sat.) /0.1 mol dm-3 NH4NO3 / test solution / ISE The ion-sensor together with double junction reference electrode was dipped in the stirred electrochemical cell. At the steady-state potentiometric response, varying concentrations of the ionic solution was injected into the cell and the new steady-state potential was recorded Selectivity of the ISE was also studied using interference of Na+ and NH+ions. The following examples are given by way of illustration of the present invention and therefore should not be construed to limit the scope of the present invention. Example: 1 Polyindole/Valinomycine based ISE: The electl'ochemical polymerization of Indole was carried out in CH2Cl3 containing 0.1 mol dm-3 TBAP and 10-3 mol dm-3 indole by sweeping potential between -0.2 to 1.1 V vs Ag/AgCl. The eleetropolymerized film was washed in CH2C12 and dried under the stream of nitrogen. The polyindole modified electrode was then conditioned in 1 mol dm3 aqueous KCl solution for 2 hrs. The solution of PVC casting membrane was made in dried THF of the composition; PVC fine powder (56 mg); valinomycin (1 mg); dibutyl phthalate (0.12 ml); tetraphenyl borate (0.75 mg); THF (2 ml). After complete, dissolution of the membrane material; 70 micro liter of the solution was added to the recessed depth of the electrode body covered with the polyindole film. The solvent (THF) was allowed to evaporate slowly over a 20h period at room temperature. This ISE has been tested for the potassium ion in the range of die typical concentrator, i.e. 1x10-6 to 5x10-1 M and were found to be very stable for several seta of measurements (as shown in Table 1-A). Interference of Na+ and NH4+ ions were also studied and ISE was found to be very selective for potassium ion. Example: 2 Polyindole/Dibenzo-18-crown-6 based ISE: The electl'ochemical polymerization of Indole was carried out as similar manner as described in 1st para of example 1. The electropolymerized film was washed in CH2C12 and dried under the stream of nitrogen. The polyindole modified electrode was then conditioned in 1 mol dm3 aqueous KCl solution for 2 h prior to the formation of ion-sensing membrane followed by drying in flowing stream of nitrogen The solution of PVC casting membrane was made in dried THF of the composition; PVC fine powder (56 mg); Dibenzo-18-crown-6 (1 mg); dibutyl phthalate (0.12 ml); tetraphenyl borate (0.75 mg); THF (2 ml). After complete dissolution of the membrane material; 70 micro liter of the solution was added to the recessed depth of the electrode body covered with the polyindole film. The solvent (THF) was allowed to evaporate slowly over a 20h period at room temperature. This ISE has been tested for the potassium ion in the range of the typical concentralons.i.e.lxl0-6 to 5x10-1 M and were found to be veiy stable for several sets of measureme-nts (as shown in Table 1-B). Interference of Na+ and NH4+ ions were also studied and ISE was found to be selective for potassium ion. Example: 3 PolycarbazoleA'alinomyeine based ISE: The electrochemical polymerization of polycarbazole was carried out in CH2C12 containing 0.1 mol dm-3 TRAP and 60mM carbazole by sweeping potential between -0.2 to 1.5 V vs Ag/AgCl. The electropolymerized film was washed in CH3Cl3 and dried under the stream of nitrogen. The polycarbazole modified electrode was then conditioned in 1 mol dm3 aqueous KCl solution for 2 h prior to the formation of ion-sensing membrane followed by drying in flowing stream of nitrogen The solution of PVC casting membrane was made in dried THF of the composition; PVC fine powder (56 mg); valinomycin (1 mg); dibutyl phthalate (0.12 ml); tetraphenyl borate (0.75 mg); THF (2 ml). After complete dissolution of the membrane material; 70 micro liter of the solution was added to the recessed depth of the electrode body covered with the polycarbazole film. The solvent (THF) was allowed to evaporate slowly over a 20h period at room temperature. This ISE has been tested for the potassium ion in the range of the typical concentratons.i.e.lxlO-6 to 5x10-1 M and were found to be very stable for several sets of measurements (as shown in Table 2-A). Interference of Na+ and NH4+ ions were also studied and ISE was found to be very selective for potassium ion. Example: 4 Polyearbazole/Dtbenzo-18-crown-6 baaed ISE: The electrochemical polymer-izalion of polycarbazole was carried out in similar manner as described in 1st para of example 3. The electropolymerized film was washed in CH2Cl2 and dried under the stream of nitrogen. The polycarbazole modified electrode was men conditioned in 1 mol dm3 aqueous KCl solution for 2 h prior to the formation of ion-sensing membrane followed by drying in flowing stream of nitrogen The solution of PVC casting membrane was made in dried THF of me composition; PVC line powder (56 mg); Dtbenzo-18-crown-6 (1 mg); dibutyl phthalate (0.12 ml); tetraphenyl borate (0.75 mg); THF (2 ml). After complete dissolution of me membrane material; 70 micro liter of the solution was added to the recessed depth of the electrode body covered with the polycarbazole film. The solvent (THF) was allowed to evaporate slowly over a 20h period at room temperature. This ISE has been tested for the potassium ion in the range of the typical concentratons.i.e.lxl0-6 to 5x10-1 M and were found to be very stable for several sets of measurements (as shown in Table 2-B). Interference of Naf and NH4+ ions were also studied and ISE was found to be very selective for potassium ion. Table 1-A (Table Removed) Table 1-B (Table Removed) Table 2-A (Table Removed) The main advantages of the present invention are: 1. No noise at the steady-state potential 2. Variation in the standard electrode potential is in a regular order. 3. Detection limit is up to 5x10-6 M of potassium ion concentration. 4. Selective towards potassium ion, nearly no interference with Na+ or NH4+ ions 5. ISE is stable up to very long time period. Claim: 1. An improved ion-selective electrode useful for sensing potassium ion in fluids which comprise a metallic part (1), the said metallic part being in direct contact with a metal foil (2) having layer of a thermally stable conducting polymer selected from polindole, polycarbazole, the said metal foil conducting polymer coated layer being provided with a layer of PVC incorporated neutral ion carrier, the said metal part, polymer coated metal foil and PVC incorporated neutral ion carrier layer being encased, if desired, by an insulating protective outer covering (3) in such a manner so as to allow fluid contact with the resultant electrode. 2. An improved ion selective electrode as claimed in claim 1, wherein the metallic part used is a non corrosive metal or alloy. 3. An improved ion selective electrode as claimed in claim 1, wherein the metal foil used may be such as Gold, Platinum, Titanium, stainless steel. 4. An improved ion selective electrode as claimed in claim, 1 wherein the PVC incorporated neutral ion carrier used may be such as Valinonmycin, various crown ethers or its derivatives like dibenzo-18-crown-6. 5. An improved ion selective electrode as claimed in claim 1, in combination with a device useful for sensing potassium ion in fluids. 6. An improved ion-selective electrode useful for sensing potassium ion in fluids substantially as herein described with reference to the examples and drawing accompanying this specification.

Documents:

2519-del-1998-abstract.pdf

2519-del-1998-claims.pdf

2519-del-1998-correspondence-others.pdf

2519-del-1998-correspondence-po.pdf

2519-del-1998-description (complete).pdf

2519-del-1998-drawings.pdf

2519-del-1998-form-1.pdf

2519-del-1998-form-19.pdf

2519-del-1998-form-2.pdf