Ion-selective layered sensor and methods of making and using the same
First Claim
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1. A sensor for the potentiometric measurement of an ion in a liquid sample, comprising:
- a dimensionally stable, chemically inert, electrically insulating, substantially planar substrate layer having disposed thereon a sensing half-cell and a reference half-cell.the sensing half-cell comprising;
(a) a terminated layer of electroconductive material in intimate contact with the substrate layer, the electroconductivity being at least 1×
102 (ohm·
cm)-1, the electroconductive material layer having coated thereon(b) a carbon layer of finely divided particles of carbon uniformly dispersed in a matrix of organic polymeric binder having coated thereon(c) an ion-selective membrane layer comprising an ionophoric material dispersed in a matrix of dielectric organic polymer, the layer having an electrical impedance at least two orders of magnitude greater than the impedance of the carbon layer, the interface between the ion-selective membrane layer and the dispersed carbon layer comprising a zone in which the layers are partially interdiffused, layers (a) and (b) being shielded from both chemical and electroconductive contact with the liquid sample;
the reference half-cell comprising;
(a) a terminated layer of electroconductive material in intimate contact with the substrate layer, the electroconductivity being at least 1×
102 (ohm·
cm)-1, the electroconductive material layer having coated thereon(b) a carbon layer of finely divided particles of carbon uniformly dispersed in a matrix of organic polymeric binder having coated thereon(c) an ion-selective membrane layer comprising an ionophoric material dispersed in a matrix of dielectric organic polymer, the layer having an electrical impedance at least two orders of magnitude greater than the impedance of the carbon layer, the interface between the ion-selective membrane layer and the dispersed carbon layer comprising a zone in which the layers are partially interdiffused, layers (a) and (b) being shielded from both chemical and electroconductive sample, the ion-selective membrane having coated thereon(d) a salt bridge layer comprising a predetermined concentration of an ion capable of interacting with the ionophoric material, the ion being dissolved in a solid hydrophilic polymer, the salt bridge layer being substantially, but incompletely, shielded from ionic contact with the liquid sample by an overlying layer of an inert liquid-impermeable electrically insulating layer to define a shielded and an unshielded surface area of the salt bridge layer.the sensing half-cell and the reference half-cell being spaced apart on the substrate layer to define a liquid sample receiving zone adapted to allow the liquid sample to make ionic contact with both the ion-selective membrane layer of the sensing half-cell and the unshielded surface area of the salt bridge layer of the reference half-cell, such that application of the liquid sample to the sensor does not substantially change the predetermined ion concentration in the salt bridge layer of the reference half-cell thereby establishing a stable reference potential.
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Abstract
A layered half cell comprising (a) an inert insulating substrate having coated thereon (b) a layer of conductive material having coated thereon (c) a layer of carbon dispersed in a dielectric polymer, the layer being coated with (d) an ion-selective membrane layer, the interface between layers (c) and (d) being partially interdiffused.
133 Citations
22 Claims
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1. A sensor for the potentiometric measurement of an ion in a liquid sample, comprising:
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a dimensionally stable, chemically inert, electrically insulating, substantially planar substrate layer having disposed thereon a sensing half-cell and a reference half-cell. the sensing half-cell comprising; (a) a terminated layer of electroconductive material in intimate contact with the substrate layer, the electroconductivity being at least 1×
102 (ohm·
cm)-1, the electroconductive material layer having coated thereon(b) a carbon layer of finely divided particles of carbon uniformly dispersed in a matrix of organic polymeric binder having coated thereon (c) an ion-selective membrane layer comprising an ionophoric material dispersed in a matrix of dielectric organic polymer, the layer having an electrical impedance at least two orders of magnitude greater than the impedance of the carbon layer, the interface between the ion-selective membrane layer and the dispersed carbon layer comprising a zone in which the layers are partially interdiffused, layers (a) and (b) being shielded from both chemical and electroconductive contact with the liquid sample; the reference half-cell comprising; (a) a terminated layer of electroconductive material in intimate contact with the substrate layer, the electroconductivity being at least 1×
102 (ohm·
cm)-1, the electroconductive material layer having coated thereon(b) a carbon layer of finely divided particles of carbon uniformly dispersed in a matrix of organic polymeric binder having coated thereon (c) an ion-selective membrane layer comprising an ionophoric material dispersed in a matrix of dielectric organic polymer, the layer having an electrical impedance at least two orders of magnitude greater than the impedance of the carbon layer, the interface between the ion-selective membrane layer and the dispersed carbon layer comprising a zone in which the layers are partially interdiffused, layers (a) and (b) being shielded from both chemical and electroconductive sample, the ion-selective membrane having coated thereon (d) a salt bridge layer comprising a predetermined concentration of an ion capable of interacting with the ionophoric material, the ion being dissolved in a solid hydrophilic polymer, the salt bridge layer being substantially, but incompletely, shielded from ionic contact with the liquid sample by an overlying layer of an inert liquid-impermeable electrically insulating layer to define a shielded and an unshielded surface area of the salt bridge layer. the sensing half-cell and the reference half-cell being spaced apart on the substrate layer to define a liquid sample receiving zone adapted to allow the liquid sample to make ionic contact with both the ion-selective membrane layer of the sensing half-cell and the unshielded surface area of the salt bridge layer of the reference half-cell, such that application of the liquid sample to the sensor does not substantially change the predetermined ion concentration in the salt bridge layer of the reference half-cell thereby establishing a stable reference potential. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A reference half-cell to be used in conjunction with a sensing half-cell for the potentiometric measurement of an ion in a liquid sample, comprising a dimensionally stable, chemically inert, electrically insulating substrate layer having coated thereon
(a) a terminated layer of electroconductive material in intimate contact with the substrate layer, the electroconductivity being at least 1× - 102 (ohm·
cm)-1, the electroconductive material layer having coated thereon;(b) a carbon layer of finely divided particles of carbon uniformly dispersed in a matrix of organic polymeric binder having coated thereon (c) an ion-selective membrane layer comprising an ionophoric material dispersed in a matrix of dielectric organic polymer, the layer having an electrical impedance at least two orders of magnitude greater than the impedance of the carbon layer, the interface between the ion-selective membrane layer and the dispersed carbon layer comprising a zone in which the layers are partially interdiffused, layers (a) and (b) being shielded from both chemical and electroconductive sample, the ion-selective membrane having coated thereon (d) a salt bridge layer comprising a predetermined concentration of an ion capable of interacting with the ionophoric material, the ion being dissolved in a solid hydrophilic polymer, the salt bridge layer being substantially, but incompletely, shielded from ionic contact with the liquid sample by an overlying layer of an inert liquid-impermeable electrically insulating layer to define a shielded and an unshielded surface area of the salt bridge layer; such that application of the liquid sample to the reference half-cell does not substantially change the predetermined ion concentration in the salt bridge layer, thereby establishing a stable reference potential. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
- 102 (ohm·
Specification