Solid state ion selective electrodes

• US 4,276,141 A
• Filed: 06/27/1979
• Issued: 06/30/1981
• Est. Priority Date: 02/24/1978
• Status: Expired due to Term

• Current Assignee: Beckman Instruments, Inc. (Danaher Corporation)
• Original Assignee: Beckman Instruments, Inc. (Danaher Corporation)
• Inventors: Hawkins, John J.
• Primary Examiner(s): Tung, T.
• Application Number:
  US06/052,639
• Time in Patent Office: 734 Days
• Field of Search: 204/1 T, 204/1 A, 204/195 M, 204/195 F, 204/195 L
• US Class Current: 204/418
• CPC Class Codes: C07F 9/12 with hydroxyaryl compounds
• CPC Class Codes: C07F 9/6533 Six-membered rings
• 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 solid state electrode for use in determining ion concentration in an aqueous solution comprising an electrically conductive element; a first lipophilic-hydrophobic (hereinafter referred to as LH) layer in intimate contact with the element; and a second LH layer in intimate contact with the first layer. The first LH layer comprises an adhesive, LH polymer having an intrinsic viscosity of from about 0.4 to about 0.9 ml/g; and an LH plasticizer. The second LH layer comprises a LH polymer having an intrinsic viscosity of from about 1 to about 1.5 ml/g; an LH plasticizer, and an LH ion-selective ligand of the ion to be determined.

Preferably, the first LH layer further comprises an LH charge carrier.

As used herein, the term "lipophilic-hydrophobic (LH)" denotes an organic solvent soluble-water insoluble substance.

Claims

1. A solid state electrode for use in determination of ion concentration in an aqueous solution comprising:

(a) an electrically conductive element;

(b) a first lipophilic-hydrophobic layer in intimate contact with said element, said first layer comprising;

(i) an adhesive, lipophilic-hydrophobic polymer having an intrinsic viscosity of from about 0.4 to about 0.9 ml/g; and

(ii) a lipophilic-hydrophobic plasticizer; and

(c) a second lipophilic-hydrophobic layer in intimate contact with said first layer, said second layer comprising;

(i) a lipophilic-hydrophobic polymer having an intrinsic viscosity of from about 1 to about 1.5 ml/g;

(ii) a lipophilic-hydrophobic plasticizer; and

(iii) a lipophilic-hydrophobic ion-selective ligand.

2. The electrode of claim 1 wherein:

(a) said electrically conductive element is selected from a group consisting of metals, metal salt coated metals, conductive carbons, conductive metal oxide coated metals, metal-group VI element compositions, compacted metal-metal salt mixtures, compacted metal-conductive metal oxide mixtures, and mixtures thereof;

(b) said first layer comprises;

(i) said adhesive, lipophilic-hydrophobic polymer selected from a group consisting of halogenated and unhalogenated aliphatic and aromatic polymers, copolymers, and terpolymers, block polymers, and grafted polymers thereof, and cycloaliphatic polymers; and

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of phthalates, adipates, trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, phosphates, phosphonates, and mixtures thereof; and

(c) said second layer comprises;

(i) a polyvinyl chloride homopolymer as said lipophilic-hydrophobic polymer;

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of phthalates, adipates, trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, phosphates, phosphonates, and mixtures thereof;

(iii) said lipophilic-hydrophobic ion selective ligand selected from a group consisting of ion selective antibiotics, ion selective macrocyclics, ion selective open chain neutral ligands, ion selective open chain ionic ligands, ion selective inorganic compounds, and mixtures thereof.

3. The electrode of claim 2 wherein:

(a) said electrically conductive element is selected from the group consisting of silver, platinum, gold, tin, indium, MX coated silver, copper oxide coated copper, silver oxide coated silver, tin oxide coated tin, reticulated carbon, compacted silver-MX mixtures, wherein M is silver and X is selected from a group consisting of halogen and group VI elements, compacted copper-copper oxide mixture, compacted silver-silver oxide mixture, compacted tin-tin oxide mixture, and mixtures thereof;

(b) said first layer comprises;

(i) said adhesive, lipophilic-hydrophobic polymer selected from a group consisting of polyvinyl chloride-ethylene copolymer, polyvinyl chloride-polypropylene copolymer, polyvinyl chloride-butylene copolymer, polyvinyl chloride-ethylhexene copolymer, polyvinyl chloride-isoprene copolymer, polyvinyl chloride-butadiene copolymer, polyvinyl chloride-vinyltoluene copolymer, polyvinyl chloride-styrene copolymer, styrene-ethylene copolymer, styrene-propylene copolymer, styrene-butylene copolymer, styrene-butadiene copolymer, styrene-ethylhexene copolymer, styrene-isoprene copolymer, and styrene-butadiene-acrylonitrile terpolymer; and

(ii) said liphophilic-hydrophobic plasticizer selected from the group consisting of dialkyl phthalates, dialkylaryl phthalates, diaryl phthalates, diarylalkyl phthalates, dialkyl adipates, dialkylaryl adipates, diaryl adipates, diarylalkyl adipates, trialkyl trimellitates, trialkylaryl trimellitates, triaryl trimellitates, triarylalkyl trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, dialkyl alkyl phosphonates, dialkyl aryl phosphonates, diaryl aryl phosphonates, diaryl alkyl phosphonates, trialkyl phosphates, trialkylaryl phosphates, triaryl phosphates, triarylalkyl phosphates, and mixtures thereof, wherein each alkyl group contains from 8 to 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(c) said second layer comprises;

(i) said polyvinyl chloride homopolymer;

(ii) said lipophilic-hydrophobic plasticizer selected from the group consisting of dialkyl phthalates, dialkylaryl phthalates, diaryl phthalates, diarylalkyl phthalates, dialkyl adipates, dialkylaryl adipates, diaryl adipates, diarylalkyl adipates, trialkyl trimellitates, trialkylaryl trimellitates, triaryl trimellitates, triarylalkyl trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, dialkyl alkyl phosphonates, dialkyl aryl phosphonates, diaryl aryl phosphonates, diaryl alkyl phosphonates, trialkyl phosphates, trialkylaryl phosphates, triaryl phosphates, triarylalkyl phosphates, and mixtures thereof, wherein each alkyl group contains from 8 to 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(iii) said liphophilic-hydrophobic ion-selective ligand.

4. The electrode of claim 3 wherein:

X is selected from a group consisting of chlorine and iodine; and

said lipophilic-hydrophobic plasticizer employed in both said first layer and said second layer is independently selected from the group consisting of dialkyl adipates, dialkylaryl adipates, diaryl adipates, diarylalkyl adipates, dialkyl alkyl phosphonates, dialkyl aryl phosphonates, diaryl aryl phosphonates, diaryl alkyl phosphonates, trialkyl phosphonates, triaryl phosphates, trialkylaryl phosphates, triarylalkyl phosphates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, and nitroaryl arylalkyl ethers, wherein said alkyl groups contain from 8 to 12 carbon atoms and are in a normal or iso -alkyl configuration.

5. The electrode of claims 1, 2, 3 or 4 wherein said first layer comprises from about 15 to about 60 weight percent of said adhesive lipophilic-hydrophobic polymer and from about 40 to about 85 weight percent of said lipophilic-hydrophobic plasticizer;

and said second layer comprises from about 20 to about 80 weight percent of said lipophilic-hydrophobic polymer, from about 40 to about 79.991 weight percent of said lipophilic-hydrophobic plasticizer; and

from about 0.009 to about 10 weight percent of said lipophilic-hydrophobic ion-selective ligand.

6. The electrode of claims 1, 2, 3 or 4 wherein said first layer comprises from about 20 to about 40 weight percent of said adhesive, lipophilic-hydrophobic polymer and from about 60 to about 80 weight percent of said lipophilic-hydrophobic plasticizer;

and said second layer comprises from about 25 to about 45 weight percent of said lipophilic-hydrophobic polymer, from about 50 to about 74.92 weight percent of said lipophilic-hydrophobic plasticizer, and from about 0.08 to about 5 weight percent of said lipophilic-hydrophobic ion-selective ligand.

7. The electrode of claims 1, 2, 3, or 4 wherein said first layer comprises from about 20 to about 30 weight percent of said adhesive, lipophilic-hydrophobic polymer and from about 70 to about 80 weight percent of said lipophilic-hydrophobic plasticizer;

and said second layer comprises from about 28 to about 32 weight percent of said lipophilic-hydrophobic polymer, from about 66.5 to about 71.9 weight percent of said lipophilic-hydrophobic plasticizer, and from about 0.1 to about 1.5 weight percent of said lipophilic-hydrophobic ion-selective ligand.

8. The electrode of claims 1, 2, 3, or 4 wherein said adhesive, lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of from about 0.5 to about 0.7 ml/g and wherein said lipophilic-hydrophobic polymer in said second layer has an intrinsic viscosity of from about 1.0 to about 1.3 ml/g.

9. The electrode of claims 1, 2, 3 or 4 wherein said adhesive, lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of about 0.6 ml/g and wherein said lipophilic-hydrophobic polymer in said second layer has an intrinsic viscosity of about 1.1 to about 1.2 ml/g.

10. The electrode of claims 1, 2, 3 or 4 for use in the determination of monovalent cation concentration in an aqueous solution wherein said second layer has a dielectric constant of from about 3 to about 4.5 at 60 cycles.

11. The solid-state electrode of claims 1, 2, 3 or 4 for use in the determination of divalent cation concentration in an aqueous solution wherein said second layer has a dielectric constant of from about 5 to about 14 at 60 cycles.

12. The electrode of claim 1 for use in the determination of potassium ion concentration in an aqueous solution comprising:

(a) said electrically conductive element selected from a group consisting of MX coated silver and compacted mixtures of silver and MX, wherein M is silver and X is selected from a group consisting of halogen and group VI elements;

(b) said first layer comprising;

(i) said adhesive, lipophilic-hydrophobic polymer selected from a group consisting of polyvinyl chloride-propylene copolymer and styrene-isoprene copolymer; and

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of dialkyl adipates and diaryl adipates, wherein each alkyl group contains from about 8 to about 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(c) said second layer comprising;

(i) a polyvinyl chloride homopolymer as said lipophilic-hydrophobic polymer;

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of dialkyl adipates and diaryl adipates, wherein each alkyl group contains from 8 to about 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(iii) said lipophilic-hydrophobic ion-selective ligand selected from a group consisting of potassium selective antibiotics, potassium selective macrocyclics, potassium selective open chain neutral ligands, potassium selective open chain ionic ligands, and potassium selective inorganic compounds, and mixtures thereof.

13. The electrode of claim 12 wherein X is selected from the group consisting of chlorine and iodine, wherein said adhesive lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of from about 0.5 to about 0.7 ml/g, wherein each of said alkyl groups contains from 8 to 12 carbon atoms;

and wherein said polyvinyl chloride homopolymer has an intrinsic viscosity of from about 1.0 to about 1.3 ml/g.

14. The electrode of claim 13 wherein X is chlorine, wherein said adhesive, lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of about 0.6 ml/g;

wherein said lipophilic-hydrophobic plasticizer in said first and second layer is dioctyl adipate;

wherein said polyvinyl chloride homopolymer has an intrinsic viscosity of from about 1.1 to about 1.2 ml/g; and

wherein said lipophilic-hydrophobic ion-selective ligand is valinomycin.

15. The electrode of claims 1, 2, 3, 4, 12 or 13 wherein said lipophilic-hydrophobic plasticizer in said first and second layers is the same.

31. The electrode of claim 1 wherein said first layer further comprises a lipophilic-hydrophobic charge carrier.

32. The electrode of claim 31 wherein:

(a) said electrically conductive element is selected from a group consisting of metals, metal salt coated metals, conductive carbons, conductive metal oxide coated metals, metal-group VI element compositions, compacted metal-metal salt mixtures, compacted metal-conductive metal oxide mixtures, and mixtures thereof;

(b) said first layer comprises;

(i) said adhesive, lipophilic-hydrophobic polymer selected from a group consisting of halogenated and unhalogenated aliphatic and aromatic polymers, copolymers, and terpolymers, block polymers, and grafted polymers thereof, and cycloaliphatic polymers;

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of phthalates, adipates, trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, phosphates, phosphonates, and mixtures thereof;

(iii) said lipophilic-hydrophobic charge carrier selected from a group consisting of ion selective antibiotics, ion selective macrocyclics, ion selective open chain neutral ligands, ion selective open chain ionic ligands, ion selective inorganic compounds, organometallic charge carriers, and mixtures thereof; and

(c) said second layer comprises;

(i) a polyvinyl chloride homopolymer as said lipophilic-hydrophobic polymer;

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of phthalates, adipates, trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, phosphates, phosphonates, and mixtures thereof;

(iii) said lipophilic-hydrophobic ion selective ligand selected from a group consisting of ion selective antibiotics, ion selective macrocyclics, ion selective open chain neutral ligands, ion selective open chain ionic ligands, ion selective inorganic compounds, and mixtures thereof.

33. The electrode of claim 32 wherein:

(a) said electrically conductive element is selected from the group consisting of silver, platinum, gold, tin, indium, MX coated silver, copper oxide coated copper, silver oxide coated silver, tin oxide coated tin, reticulated carbon, compacted silver-MX mixtures, wherein M is silver and X is selected from a group consisting of halogen and group VI elements, compacted copper-copper oxide mixture, compacted silver-silver oxide mixture, compacted tin-tin oxide mixture, and mixtures thereof;

(b) said first layer comprises;

(i) said adhesive, lipophilic-hydrophobic polymer selected from a group consisting of polyvinyl chloride-ethylene copolymer, polyvinyl chloride-polypropylene copolymer, polyvinyl chloride-butylene copolymer, polyvinyl chloride-ethylhexene copolymer, polyvinyl chloride-isoprene copolymer, polyvinyl chloride-butadiene copolymer, polyvinyl chloride-vinyltoluene copolymer, polyvinyl chloride-styrene copolymer, styrene-ethylene copolymer, styrene-propylene copolymer, styrene-butylene copolymer, styrene-butadiene copolymer, styrene-ethylhexene copolymer, and styrene-butadiene-acrylonitrile terpolymer;

(ii) said lipophilic-hydrophobic plasticizer selected from the group consisting of dialkyl phthalates, dialkylaryl phthalates, diaryl phthalates, diarylalkyl phthalates, dialkyl adipates, dialkylaryl adipates, diaryl adipates, diarylalkyl adipates, trialkyl trimellitates, trialkylaryl trimellitates, triaryl trimellitates, triarylalkyl trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, dialkyl alkyl phosphonates, dialkyl aryl phosphonates, diaryl aryl phosphonates, diaryl alkyl phosphonates, trialkyl phosphates, trialkylaryl phosphates, triaryl phosphates, triarylalkyl phosphates, and mixtures thereof, wherein each alkyl group contains from 8 to 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(iii) said lipophilic-hydrophobic charge carrier; and

(c) said second layer comprises;

(i) said polyvinyl chloride homopolymer;

(ii) said lipophilic-hydrophobic plasticizer selected from the group consisting of dialkyl phthalates, dialkylaryl phthalates, diaryl phthalates, diarylalkyl phthalates, dialkyl adipates, dialkylaryl adipates, diaryl adipates, diarylalkyl adipates, trialkyl trimellitates, trialkylaryl trimellitates, triaryl trimellitates, triarylalkyl trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, dialkyl alkyl phosphonates, dialkyl aryl phosphonates, diaryl aryl phosphonates, diaryl alkyl phosphonates, trialkyl phosphates, trialkylaryl phosphates, triaryl phosphates, triarylalkyl phosphates, and mixtures thereof, wherein each alkyl group contains from 8 to 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(iii) said lipophilic-hydrophobic ion-selective ligand.

34. The electrode of claim 33 wherein X is selected from a group consisting of chlorine and iodine;

and

said lipophilic-hydrophobic plasticizer employed in both said first and said second layer is independently selected from the group consisting of trialkyl trimellitates, trialkylaryl trimellitates, triaryl trimellitates, triarylalkyl trimellitates, dialkyl alkyl phosphonates, dialkyl aryl phosphonates, diaryl aryl phosphonates, diaryl alkyl phosphonates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, and nitroaryl arylalkyl ethers, wherein said alkyl groups contain 8 to 12 carbon atoms and are in a normal or iso- alkyl configuration.

35. The electrode of claims 31, 32, 33 or 34 wherein said first layer comprises from about 15 to about 85 weight percent of said adhesive lipophilic-hydrophobic polymer, from about 10 to about 84.99 weight percent of said lipophilic-hydrophobic plasticizer, and from about 0.01 to about 5 weight percent of said lipophilic-hydrophobic charge carrier;

and said second layer comprises from about 20 to about 80 weight percent of said liphophilic-hydrophobic polymer, from about 40 to about 79.991 weight percent of said lipophilic-hydrophobic plasticizer; and

from about 0.009 to about 10 weight percent of said lipophilic-hydrophobic ion-selective ligand.

36. The electrode of claims 31, 32, 33, or 34 wherein said first layer comprises from about 20 to about 35 weight percent of said adhesive, lipophilic-hydrophobic polymer, from about 62.5 to about 79.5 weight percent of said lipophilic-hydrophobic plasticizer, and from about 0.05 to about 2.5 weight percent of said lipophilic-hydrophobic charge carrier;

and said second layer comprises from about 25 to about 45 weight percent of said lipophilic-hydrophobic polymer, from about 50 to about 74.92 weight percent of said lipophilic-hydrophobic plasticizer, and from about 0.08 to about 5 weight percent of said lipophilic-hydrophobic ion-selective ligand.

37. The electrode of claims 31, 32, 33 or 34 wherein said first layer comprises from about 20 to about 30 weight percent of said adhesive, lipophilic-hydrophobic polymer, from about 69 to about 79.92 weight percent of said lipophilic-hydrophobic plasticizer, and from about 0.08 to about 1 weight percent of said lipophilic-hydrophobic charge carrier;

and said second layer comprises from about 28 to about 32 weight percent of said lipophilic-hydrophobic polymer, from about 66.5 to about 71.9 weight percent of said lipophilic-hydrophobic plasticizer, and from about 0.1 to about 1.5 weight percent of said lipophilic-hydrophobic ion-selective ligand.

38. The electrode of claims 31-33 or 34 wherein said adhesive, lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of from about 0.5 to about 0.7 ml/g and wherein said lipophilic-hydrophobic polymer in said second layer has an intrinsic viscosity of from about 1.0 to about 1.3 ml/g.

39. The electrode of claims 31-33 or 34 wherein said adhesive, lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of about 0.6 ml/g and wherein said lipophilic-hydrophobic polymer in said second layer has an intrinsic viscosity of about 1.1 to about 1.2 ml/g.

40. The electrode of claims 31-33 or 34 for use in the determination of monovalent cation concentration in an aqueous solution wherein said second layer has a dielectric constant of from about 3 to about 4.5 at 60 cycles.

41. The solid-state electrode of claims 31, 32, 33 or 34 for use in the determination of divalent cation concentration in an aqueous solution wherein said second layer has a dielectric constant of from about 5 to about 14 at 60 cycles.

42. The electrode of claim 31 for use in the determination of potassium ion concentration in an aqueous solution comprising:

(a) said electrically conductive element selected from a group consisting of MX coated silver and compacted mixtures of silver and MX, wherein M is silver and X is selected from a group consisting of halogen and group VI elements;

(b) said first layer comprising;

(i) said adhesive, lipophilic-hydrophobic polymer selected from a group consisting of polyvinyl chloride-propylene copolymer and styrene-isoprene copolymer;

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of trialkyl trimellitates, trialkylaryl trimellitates, triaryl trimellitates, and triarylalkyl trimellitates, wherein each alkyl group contains from about 8 to about 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(iii) said lipophilic-hydrophobic charge carrier; and

(c) said second layer comprising;

(i) polyvinyl chloride homopolymer as said lipophilic-hydrophobic polymer;

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of trialkyl trimellitates, trialkylaryl trimellitates, triaryl trimellitates, and triarylalkyl trimellitates, wherein each alkyl group contains from 8 to about 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(iii) said lipophilic-hydrophobic ion-selective ligand selected from a group consisting of potassium selective antibiotics, potassium selective macrocylics, potassium selective open chain neutral ligands, potassium selective open chain ionic ligands, potassium selective inorganic compounds, and mixtures thereof.

43. The electrode of claim 42 wherein X is selected from the group consisting of chlorine and iodine, wherein said adhesive lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of from about 0.5 to about 0.7 ml/g, wherein each of said alkyl groups contains from 8 to 12 carbon atoms;

and wherein said polyvinyl chloride homopolymer has an intrinsic viscosity of from about 1.0 to about 1.3 ml/g.

44. The electrode of claim 43 wherein X is chlorine, wherein said adhesive, lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of about 0.6 ml/g;

wherein said lipophilic-hydrophobic plasticizer in said first and second layer is selected from the group consisting of trioctyl trimellitate, triisononyl trimellitate, tri-n-nonyl trimellitate, triphenyl trimellitate, trioctylphenyl trimellitate, and tridecylphenyl trimellitate;

wherein said polyvinyl chloride homopolymer has an intrinsic viscosity of from about 1.1 to about 1.2 ml/g; and

wherein said ion-selective ligand is valinomycin.

45. The electrode of claim 44 wherein said lipophilic-hydrophobic charge carrier is valinomycin.

16. A membrane for use in determination of ion concentration in an aqueous solution comprising:

(a) a first lipophilic-hydrophobic layer comprising;

(i) an adhesive, lipophilic-hydrophobic polymer having an intrinsic viscosity of from about 0.4 to about 0.9 ml/g; and

(ii) an lipophilic-hydrophobic plasticizer; and

(c) a second lipophilic-hydrophobic layer in intimate contact with said first layer, said second layer comprising;

(i) a lipophilic-hydrophobic polymer having an intrinsic viscosity of from about 1 to about 1.5 ml/g;

(ii) a lipophilic-hydrophobic plasticizer; and

(iii) a lipophilic-hydrophobic ion-selective ligand.

17. The membrane of claim 16 wherein:

(a) said first layer comprises;

(i) said adhesive, lipophilic-hydrophobic polymer selected from a group consisting of halogenated and unhalogentated aliphatic and aromatic polymers, copolymers, and terpolymers, block polymers, and grafted polymers thereof, and cycloaliphatic polymers; and

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of phthalates, adipates, trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, phosphates, phosphonates, and mixtures thereof; and

(b) said second layer comprises;

(i) a polyvinyl chloride homopolymer as said lipophilic-hydrophobic polymer;

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of phthalates, adipates, trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, phosphates, phosphonates, and mixtures thereof;

(iii) said lipophilic-hydrophobic ion selective ligand selected from a group consisting of ion selective antibiotics, ion selective macrocyclics, ion selective open chain neutral ligands, ion selective open chain ionic ligands, ion selective inorganic compounds, and mixtures thereof.

18. The membrane of claim 17 wherein:

(a) said first layer comprises;

(i) said adhesive, lipophilic-hydrophobic polymer selected from a group consisting of polyvinyl chloride-ethylene copolymer, polyvinyl chloride-polypropylene copolymer, polyvinyl chloride-butylene copolymer, polyvinyl chloride-ethylhexene copolymer, polyvinyl chloride-isoprene copolymer, polyvinyl chloride-butadiene copolymer, polyvinyl chloride-vinyltoluene copolymer, polyvinyl chloride-styrene copolymer, styrene-ethylene copolymer, styrene-propylene copolymer, styrene-butylene copolymer, styrene-butadiene copolymer, styrene-ethylhexene copolymer, styrene-isoprene copolymer, and styrene-butadiene-acrylonitrile terpolymer; and

(ii) said liphophilic-hydrophobic plasticizer selected from the group consisting of dialkyl phthalates, dialkylaryl phthalates, diaryl phthalates, diarylalkyl phthalates, dialkyl adipates, dialkylaryl adipates, diaryl adipates, diarylalkyl adipates, trialkyl trimellitates, trialkylaryl trimellitates, triaryl trimellitates, triarylalkyl trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, dialkyl alkyl phosphonates, dialkyl aryl phosphonates, diaryl aryl phosphonates, diaryl alkyl phosphonates, trialkyl phosphates, trialkylaryl phosphates, triaryl phosphates, triarylalkyl phosphates, and mixtures thereof, wherein each alkyl group contains from 8 to 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(b) said second layer comprises;

(i) said polyvinyl chloride homopolymer;

(ii) said lipophilic-hydrophobic plasticizer selected from the group consisting of dialkyl phthalates, dialkylalkyl phthalates, diaryl phthalates, diarylalkyl phthalates, dialkyl adipates, dialkylaryl adipates, diaryl adipates, diarylalkyl adipates, trialkyl trimellitates, trialkylaryl trimellitates, triaryl trimellitates, triarylalkyl trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, dialkyl alkyl phosphonates, dialkyl aryl phosphonates, diaryl aryl phosphonates, diaryl alkyl phosphonates, trialkyl phosphates, trialkylaryl phosphates, triaryl phosphates, triarylalkyl phosphates, and mixtures thereof, wherein each alkyl group contains from 8 to 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(iii) said lipophilic-hydrophobic ion-selective ligand.

19. The membrane of claim 18 wherein:

said lipophilic-hydrophobic plasticizer employed in both said first layer and said second layer is independently selected from the group consisting of dialkyl adipates, dialkylaryl adipates, diaryl adipates, diarylalkyl adipates, dialkyl alkyl phosphonates, dialkyl aryl phosphonates, diaryl aryl phosphonates, diaryl alkyl phosphonates, trialkyl phosphates, triaryl phosphates, trialkylaryl phosphates, triarylalkyl phosphates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, and nitroaryl arylalkyl ethers, wherein said alkyl groups contain from 8 to 12 carbon atoms and are in a normal or iso- alkyl configuration.

20. The membrane of claims 16, 17, 18, or 19 wherein said first layer comprises from about 15 to about 60 weight percent of said adhesive lipophilic-hydrophobic polymer and from about 40 to about 85 weight percent of said lipophilic-hydrophobic plasticizer;

and said second layer comprises from about 20 to about 80 weight percent of said lipophilic-hydrophobic polymer, from about 40 to about 79.991 weight percent of said lipophilic-hydrophobic plasticizer; and

from about 0.009 to about 10 weight percent of said lipophilic-hydrophobic ion-selective ligand.

21. The membrane of claims 16, 17, 18, or 19 wherein said first layer comprises from about 20 to about 40 weight percent of said adhesive, lipophilic-hydrophobic polymer and from about 60 to about 80 weight percent of said lipophilic-hydrophobic plasticizer;

and said second layer comprises from about 25 to about 45 weight percent of said lipophilic-hydrophobic polymer, from about 50 to about 74.92 weight percent of said lipophilic-hydrophobic plasticizer, and from about 0.08 to about 5 weight percent of said lipophilic-hydrophobic ion-selective ligand.

22. The membrane of claims 16, 17, 18 or 19 wherein said first layer comprises from about 20 to about 30 weight percent of said adhesive, lipophilic-hydrophobic polymer and from about 70 to about 80 weight percent of said lipophilic-hydrophobic plasticizer;

and said second layer comprises from about 28 to about 32 weight percent of said lipophilic-hydrophobic polymer, from about 66.5 to about 71.9 weight percent of said lipophilic-hydrophobic plasticizer, and from about 0.1 to about 1.5 weight percent of said lipophilic-hydrophobic ion-selective ligand.

23. The membrane of claims 16-18 or 19 wherein said adhesive, lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of from about 0.5 to about 0.7 ml/g and wherein said lipophilic-hydrophobic polymer in said second layer has an intrinsic viscosity of from about 1.0 to about 1.3 ml/g.

24. The membrane of claims 16-18 or 19 wherein said adhesive, lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of about 0.6 ml/g and wherein said lipophilic-hydrophobic polymer in said second layer has an intrinsic viscosity of about 1.1 to about 1.2 ml/g.

25. The membrane of claims 16-18 or 19 for use in the determination of monovalent cation concentration in an aqueous solution wherein said second layer has a dielectric constant of from about 3 to about 4.5 at 60 cycles.

26. The membrane of claims 16-18 or 19 for use in the determination of divalent cation concentration in an aqueous solution wherein said second layer has a dielectric constant of from about 5 to about 14 at 60 cycles.

27. The membrane of claim 16 for use in the determination of potassium ion concentration in an aqueous solution comprising:

(a) said first layer comprising;

(i) said adhesive, lipophilic-hydrophobic polymer selected from a group consisting of polyvinyl chloride-propylene copolymer and styrene-isoprene copolymer; and

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of dialkyl adipates and diaryl adipates, wherein each alkyl group contains from about 8 to about 14 carbon atoms; and

each aryl group contains from 6 to 12 carbon atoms; and

(b) said second layer comprising;

(i) a polyvinyl chloride homopolymer as said lipophilic-hydrophobic polymer

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of dialkyl adipates and diaryl adipates, wherein each alkyl group contains from 8 to about 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(iii) said lipophilic-hyodrophobic ion-selective ligand selected from a group consisting of potassium selective antiobiotics, potassium selective macrocylics, potassium selective open chain neutral ligands, potassium selective open chain ionic ligands, and potassium selective inorganic compounds, and mixtures thereof.

28. The membrane of claim 27 wherein said adhesive lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of from about 0.5 to about 0.7 ml/g, wherein each of said alkyl groups contains from 8 to 12 carbon atoms;

and wherein said polyvinyl chloride homopolymer has an intrinsic viscosity of from about 1.0 to about 1.3 ml/g.

29. The membrane of claim 28 wherein said adhesive, lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of about 0.6 ml/g;

wherein said lipophilic-hydrophobic plasticizer in said first and second layer is dioctyl adipate;

wherein said polyvinyl chloride homopolymer has an intrinsic viscosity of from about 1.1 to about 1.2 ml/g; and

wherein said lipophilic-hydrophobic ion-selective ligand is valinomycin.

30. The membrane of claims 16, 17, 18, 19, 27, or 28 wherein said lipophilic-hydrophobic plasticizer in said first and second layers is the same.

46. A membrane for use in determination of ion concentrations in an aqueous solution comprising:

(a) a first lipophilic-hydrophobic layer comprising;

(i) an adhesive, lipophilic-hydrophobic polymer having an intrinsic viscosity of from about 0.4 to about 0.9 ml/g;

(ii) a lipophilic-hydrophobic plasticizer; and

(iii) a lipophilic-hydrophobic charge carrier; and

(b) a second lipophilic-hydrophobic layer in intimate contact with said first layer, said second layer comprising;

(i) a lipophilic-hydrophobic polymer having an intrinsic viscosity of from about 1 to about 1.5 ml/g;

(ii) a lipophilic-hydrophobic plasticizer; and

(iii) a lipophilic-hydrophobic ion-selective ligand.

47. The membrane of claim 46 wherein:

(a) said first layer comprises;

(i) said adhesive, lipophilic-hydrophobic polymer selected from a group consisting of halogenated and unhalogenated aliphatic and aromatic polymers, copolymers, and terpolymers, block polymers, and grafted polymers thereof, and cycloaliphatic polymers;

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of phthalates, adipates, trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, phosphates, phosphonates, and mixtures thereof;

(iii) said lipophilic-hydrophobic charge carrier selected from a group consisting of ion selective antibiotics, ion selective macrocyclics, ion selective open chain neutral ligands, ion selective open chain ionic ligands, ion selective inorganic compounds, organometallic charge carriers, and mixtures thereof; and

(b) said second layer comprises;

(i) a polyvinyl chloride homopolymer as said lipophilic-hydrophobic polymer;

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of phthalates, adipates, trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, phosphates, phosphonates, and mixtures thereof;

(iii) said lipophilic-hydrophobic ion selective ligand selected from a group consisting of ion selective antibiotics, ion selective macrocyclics, ion selective open chain neutral ligands, ion selective open chain ionic ligands, ion selective inorganic compounds, and mixtures thereof.

48. The membrane of claim 47 wherein:

(a) said first layer comprises;

(i) said adhesive, lipophilic-hydrophobic polymer selected from a group consisting of polyvinyl chloride-ethylene copolymer, polyvinyl chloride-polypropylene copolymer, polyvinyl chloride-butylene copolymer, polyvinyl chloride-ethylhexane copolymer, polyvinyl chloride-isoprene copolymer, polyvinyl chloride-butadiene copolymer, polyvinyl chloride-vinyltoluene copolymer, polyvinyl chloride-styrene copolymer, styrene-ethylene copolymer, styrene-propylene copolymer, styrene-butylene copolymer, styrene-butadiene copolymer, styrene-ethylhexane copolymer, and styrene-butadiene-acrylonitrile terpolymer;

(ii) said lipophilic-hydrophobic plasticizer selected from the group consisting of dialkyl phthalates, dialkylaryl phthalates, diaryl phthalates, diarylalkyl phthalates, dialkyl adipates, dialkylaryl adipates, diaryl adipates, diarylalkyl adipates, trialkyl trimellitates, trialkylaryl trimellitates, triaryl trimellitates, triarylalkyl trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, dialkyl alkyl phosphonates, dialkyl aryl phosphonates, diaryl aryl phosphonates, diaryl alkyl phosphonates, trialkyl phosphates, trialkylaryl phosphates, triaryl phosphates, triarylalkyl phosphates, and mixtures thereof, wherein each alkyl group contains from 8 to 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(iii) said lipophilic-hydrophobic charge carrier; and

(b) said second layer comprises;

(i) said polyvinyl chloride homopolymer;

(ii) said lipophilic-hydrophobic plasticizer selected from the group consisting of dialkyl phthalates, dialkylaryl phthalates, diaryl phthalates, diarlalkyl phthalates, dialkyl adipates, dialkylaryl adipates, diaryl adipates diarylalkyl adipates, trialkyl trimellitates, trialkylaryl trimellitates, triaryl trimellitates, triarylalkyl trimellitates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, nitroaryl arylalkyl ethers, dialkyl alkyl phosphonates, dialkyl aryl phosphonates, diaryl aryl phosphonates, diaryl alkyl phosphonates, trialkyl phosphates, trialkylaryl phosphates, triaryl phosphates, triarylalkyl phosphates, and mixtures thereof, wherein each alkyl group contains from 8 to 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(iii) said lipophilic-hydrophobic ion-selective ligand.

49. The membrane of claim 48 wherein:

said lipophilic-hydrophobic plasticizer employed in both said first and said second layer is independently selected from the group consisting of trialkyl trimellitates, trialkylaryl trimellitates, triaryl trimellitates, triarylalkyl trimellitates, dialkyl alkyl phosphonates, dialkyl aryl phosphonates, diaryl aryl phosphonates, diaryl alkyl phosphonates, nitroaryl alkyl ethers, nitroaryl alkylaryl ethers, and nitroaryl arylalkyl ethers, wherein said alkyl groups contain 8 to 12 carbon atoms and are in a normal or iso-alkyl configuration.

50. The membrane of claims 46, 47, 48 or 49 wherein said first layer comprises from about 15 to about 85 weight percent of said adhesive lipophilic-hydrophobic polymer, from about 10 to about 84.99 weight percent of said lipophilic-hydrophobic plasticizer, and from about 0.01 to about 5 weight percent of said lipophilic-hydrophobic charge carrier;

and said second layer comprises from about 20 to about 80 weight percent of said lipophilic-hydrophobic polymer, from about 40 to about 79.991 weight percent of said lipophilic-hydrophobic plasticizer; and

from about 0.009 to about 10 weight percent of said lipophilic-hydrophobic ion-selective ligand.

51. The membrane of claims 46, 47, 48 or 49 wherein said first layer comprises from about 20 to about 35 weight percent of said adhesive, lipophilic-hydrophobic polymer, from about 62.5 to about 79.5 weight percent of said lipophilic-hydrophobic plasticizer, and from about 0.05 to about 2.5 weight percent of said lipophilic-hydrophobic charge carrier;

and said second layer comprises from about 25 to about 45 weight percent of said lipophilic-hydrophobic polymer, from about 50 to about 74.92 weight percent of said lipophilic-hydrophobic plasticizer, and from about 0.08 to about 5 weight percent of said lipophilic-hydrophobic ion-selective ligand.

52. The membrane of claims 46, 47, 48 or 49 wherein said first layer comprises from about 20 to about 30 weight percent of said adhesive, lipophilic-hydrophobic polymer, from about 69 to about 79.92 weight percent of said lipophilic-hydrophobic plasticizer, and from about 0.08 to about 1 weight percent of said lipophilic-hydrophobic charge carrier;

and said second layer comprises from about 28 to about 32 weight percent of said lipophilic-hydrophobic polymer, from about 66.5 to about 71.9 weight percent of said lipophilic-hydrophobic plasticizer, and from about 0.1 to about 1.5 weight percent of said lipophilic-hydrophobic ion-selective ligand.

53. The membrane of claims 46, 47, 48 or 49 wherein said adhesive, lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of from about 0.5 to about 0.7 ml/g and wherein said lipophilic-hydrophobic polymer in said second layer has an intrinsic viscosity of from about 1.0 to about 1.3 ml/g.

54. The membrane of claims 46, 47, 48 or 49 wherein said adhesive, lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of about 0.6 ml/g and wherein said lipophilic-hydrophobic polymer in said second layer has an intrinsic viscosity of about 1.1 to about 1.2 ml/g.

55. The membrane of claims 46, 47, 48 or 49 for use in the determination of monovalent cation concentration in an aqueous solution wherein said second layer has a dielectric constant of from about 3 to about 4.5 at 60 cycles.

56. The membrane of claims 46, 47, 48 or 49 for use in the determination of divalent cation concentration in an aqueous solution wherein said second layer has a dielectric constant of from about 5 to about 14 at 60 cycles.

57. The membrane of claim 46 for use in the determination of potassium ion concentration in an aqueous solution comprising:

(a) said first layer comprising;

(i) said adhesive, lipophilic-hydrophobic polymer selected from a group consisting of polyvinyl chloride-propylene copolymer and styrene-isoprene copolymer;

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of trialkyl trimellitates, trialkylaryl trimellitates, triaryl trimellitates, and triarylalkyl trimellitates, wherein each alkyl group contains from about 8 to about 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(iii) said lipophilic-hydrophobic charge carrier; and

(b) said second layer comprising;

(i) a polyvinyl chloride homopolymer as said lipophilic-hydrophobic polymer;

(ii) said lipophilic-hydrophobic plasticizer selected from a group consisting of trialkyl, trimellitates, trialkylaryl trimellitates, triaryl trimellitates, and triarylalkyl trimellitates, wherein each alkyl group contains from 8 to about 14 carbon atoms and each aryl group contains from 6 to 12 carbon atoms; and

(iii) said lipophilic-hydrophobic ion-selective ligand selected from a group consisting of potassium selective antibiotics, potassium selective macrocylics;

potassium selective opn chain neutral ligands, potassium selective open chain ionic ligands, potassium selective inorganic compounds, and mixtures thereof.

58. The membrane of claim 57 wherein said adhesive lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of from about 0.5 to about 0.7 ml/g, wherein each of said alkyl groups contains from 8 to 12 carbon atoms;

and wherein said polyvinyl chloride homopolymer has an intrinsic viscosity of from about 1.0 to about 1.3 ml/g.

59. The membrane of claim 58 wherein said adhesive, lipophilic-hydrophobic polymer in said first layer has an intrinsic viscosity of about 0.6 ml/g;

wherein said lipophilic-hydrophobic plasticizer in said first and second layer is selected from a group consisting of trioctyl trimellitate, triisononyl trimellitate, tri-n-nonyl trimellitate, triphenyl trimellitate, trioctylphenyl trimellitate, and tridecylphenyl trimellitate;

wherein said polyvinyl chloride homopolymer has an intrinsic viscosity of from about 1.1 to about 1.2 ml/g; and

wherein said ion-selective ligand is valinomycin.

60. The membrane of claim 59 wherein said lipophilic-hydrophobic charge carrier is valinomycin.