Material for establishing solid state contact for ion selective electrodes

• US 5,911,862 A
• Filed: 09/08/1997
• Issued: 06/15/1999
• Est. Priority Date: 09/15/1993
• Status: Expired due to Term

• Current Assignee: Siemens Healthcare Diagnostics Incorporated (Siemens AG)
• Original Assignee: Chiron Corporation (Bayer AG)
• Inventors: Chan, Andy D. C.
• Primary Examiner(s): TUNG, TA HSUNG
• Application Number:
  US08/929,195
• Time in Patent Office: 645 Days
• Field of Search: 204/415, 204/416, 204/418, 204/419
• US Class Current: 204/418
• CPC Class Codes: G01N 27/3335 the membrane containing at least one organic component G01N27/3271 takes precedence; aspects concerning the enzyme reagent in enzyme electrodes C12Q1/001
• CPC Class Codes: G01N 27/414 Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS

Abstract

A polymeric material which to form a stable, reproducible interface between the ionic and electronic domains of an ion selective sensor, or an ion selective field effect transistor, or the like is provided. When employed in an ion selective sensor, the polymeric material is advantageously provided over a solid internal reference electrode and an ion selective membrane is provided thereover. According to one embodiment, the polymeric material of the invention includes less than about 1.63×10²¹ immobilized charged sites per gram (less than about 2.72 millaequivalents/gram). According to another embodiment, the polymeric material includes immobilized sites of charge opposite that of mobile ions involved in the redox couple. A preferred polymeric material comprises a copolymer of methacrylamidopropyltrimethylammoniumchloride and methylmethacrylate. In a particularly advantageous embodiment, the ion selective membrane has little or no plasticizer.

Claims

1. An ion selective solid state sensor, comprising:

an electrically conductive material providing a reference redox couple, said electrically conductive material including mobile ions having a first charge;

an acrylic polymeric material having immobilized ions and being in direct contact with said electrically conductive material, said immobilized ions having a second charge opposite said first charge, said acrylic polymeric material being provided on said electrically conductive material; and

an ion selective membrane covering said polymeric material, said ion selective membrane comprising an ethylene vinyl acetate polymer, said ethylene vinyl acetate polymer including from about 30 weight percent to about 75 weight percent vinyl acetate monomer and from about 0 percent to about 20 percent by weight plasticizer, and an ion selective material dispersed within said ethylene vinyl acetate polymer, wherein said ion selective membrane is from about 0 percent crystalline to about 10 percent crystalline, and wherein said ion selective membrane is not in direct physical contact with said electrically conductive material but is in contact with said acrylic polymeric material.

2. An ion selective sensor in accordance with claim 1, wherein said ethylene vinyl acetate polymer includes from about 35 weight percent to about 55 weight percent vinyl acetate monomer and from about 0 percent to about 5 percent by weight plasticizer.

3. An ion selective sensor in accordance with claim 2, wherein said ethylene vinyl acetate polymer is substantially devoid of plasticizer.

4. An ion selective sensor in accordance with claims 1, 2 or 3, wherein said ethylene vinyl acetate polymer includes from about 40 weight percent to about 50 weight percent vinyl acetate monomer.

5. An ion selective sensor in accordance with claims 1, 2 or 3, wherein said ethylene vinyl acetate polymer includes about 45 weight percent vinyl acetate monomer.

6. An ion selective sensor in accordance with claim 2, wherein said membrane comprises from about 0.1 percent to about 10 percent of said ion selective material by weight.

7. An ion selective sensor in accordance with claim 6, wherein said membrane comprises from about 1 percent to about 6 percent of said ion selective material by weight.

8. An ion selective sensor in accordance with claims 1, 2 or 3, wherein said ion selective membrane further comprises a salt uniformly incorporated in said membrane, said salt having a mole percent of said membrane so as to permit increased ion transport within said membrane.

9. An ion selective sensor in accordance with claim 8, wherein said mole percent of said salt is from about 10 percent to about 80 percent of said mole percent of said ion selective material.

10. An ion selective sensor in accordance with claim 8, wherein said mole percent of said salt is from about 33 percent to about 66 percent of said mole percent of said ion selective material.

11. An ion selective sensor in accordance with claims 1, 2 or 3, wherein said membrane has a slope of at least about 50 millivolts per decade of analyte concentration.

12. An ion selective sensor in accordance with claims 1, 2 or 3, wherein said membrane has a slope of at least about 55 millivolts per decade of analyte concentration.

13. An ion selective sensor in accordance with claims 1, 2 or 3, wherein said membrane is from about 0% crystalline to about 5% crystalline.

14. An ion selective sensor in accordance with claims 1, 2 or 3, wherein said membrane is from about 0% crystalline to about 3% crystalline.

15. An ion selective sensor in accordance with claim 1, further comprising:

polyvinyl chloride polymer combined with said ethylene vinyl acetate polymer, wherein said membrane comprises from about 0.1 percent to about 50 percent by weight of said polyvinyl chloride polymer.

16. A chemical responsive solid state field effect transducer, comprising:

a layer of semiconductor material having a surface;

a pair of first diffusion regions of a first doping characteristic at said surface, a region of said surface of said layer of semiconductor material existing between said pair of first diffusion regions;

a second diffusion region of a second doping characteristic at said region of said surface of said layer of semiconductive material existing between said pair of first diffusion regions;

an electrically insulating material provided at said region of said surface of said layer of semiconductor material existing between said pair of first diffusion regions;

an acrylic polymeric material in direct contact with said diffusion regions and, having immobilized charged sites provided on said electrically insulating material, said acrylic polymeric material carrying less than about 1.63×

10²¹ immobilized charged sites per gram, said acrylic polymeric material separated from said diffusion regions by said insulating material;

an ion selective membrane provided in direct contact on said acrylic polymeric material, said ion selective membrane comprising an ethylene vinyl acetate polymer including from about 30 weight percent to about 75 weight percent vinyl acetate monomer and from about 0 percent to about 20 percent by weight plasticizer, and an ion selective material dispersed within said ethylene vinyl acetate polymer, wherein said ion selective membrane is from about 0 percent crystalline to about 10 percent crystalline; and

an electrically insulating encapsulant sealing said transducer at a sample region while leaving exposed a region of said ion selective membrane for exposure to a sample, wherein said acrylic polymeric material in not in direct physical contact with said sample.

17. An transducer in accordance with claim 16, wherein said ethylene vinyl acetate polymer includes from about 35 weight percent to about 55 weight percent vinyl acetate monomer and from about 0 percent to about 5 percent by weight plasticizer.

18. A transducer in accordance with claim 17, wherein said ethylene vinyl acetate polymer is substantially devoid of plasticizer.

19. A transducer in accordance with claim 16, wherein said ethylene vinyl acetate polymer includes from about 40 weight percent to about 50 weight percent vinyl acetate monomer.

20. A transducer in accordance with claim 16, wherein said ethylene vinyl acetate polymer includes about 45 weight percent vinyl acetate monomer.

21. A transducer in accordance with claim 16, wherein said membrane comprises from about 0.1 percent to about 10 percent of said ion selective material by weight.

22. A transducer in accordance with claim 21, wherein said membrane comprises from about 1 percent to about 6 percent of said ion selective material by weight.

23. A transducer in accordance with claim 16, wherein said membrane further comprises a salt uniformly incorporated in said membrane, said salt having a mole percent of said membrane so as to permit increased ion transport within said membrane.

24. A transducer in accordance with claim 23, wherein said mole percent of said salt is from about 10 percent to about 80 percent of said mole percent of said ion selective material.

25. A transducer in accordance with claim 23, wherein said mole percent of said salt is from about 33 percent to about 66 percent of said mole percent of said ion selective material.

26. A transducer in accordance with claim 16, wherein said membrane has a slope of at least about 50 millivolts per decade of analyte concentration.

27. A transducer in accordance with claim 16, wherein said membrane has a slope of at least about 55 millivolts per decade of analyte concentration.

28. A transducer in accordance with claim 16, wherein said membrane is from about 0% crystalline to about 5% crystalline.

29. A transducer in accordance with claim 16, wherein said membrane is from about 0% crystalline to about 3% crystalline.

30. A transducer in accordance with claim 16, wherein said membrane further comprises polyvinyl chloride polymer combined with said ethylene vinyl acetate polymer, wherein said membrane comprises from about 0.1 percent to about 50 percent by weight said polyvinyl chloride polymer.