Immobilized electrochemical cell devices and methods of manufacture

• US 4,783,250 A
• Filed: 02/12/1987
• Issued: 11/08/1988
• Est. Priority Date: 08/21/1979
• Status: Expired due to Fees

• Current Assignee: Pons B. Stanley, Seyed J. Ghoroghchian
• Original Assignee: Pons B. Stanley, Seyed J. Ghoroghchian
• Inventors: Pons, B. Stanley, Ghoroghchian, Seyed J.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/013,691
• Time in Patent Office: 635 Days
• Field of Search: 204/400, 204/403, 204/1 T, 204/1 K, 204/412, 128/635, 427/125
• US Class Current: 204/400
• CPC Class Codes: G01N 27/4035 Combination of a single ion-sensing electrode and a single reference electrode G01N27/406 and G01N27/413 take precedence

Abstract

Devices and methods for providing electrochemical cells are disclosed which can be used in virtually any gaseous or liquid environment to make electrochemical determinations. The electrochemical cell comprises a microelectrode and a large reference electrode which are positioned a very short distance apart. The space between the microelectrode and the reference electrode is filled with a highly resistant material which has been treated (or otherwise provided) with an ionic substance. In use, the ionic substance associated with the resistive material acts as an immobilized ionic solution in much the same way as an electrolyte in a conventional electrochemical cell. However, the relative size and positioning of the microelectrode and the reference electrode overcame the problems of the prior art so that sensitive, accurate measurements can be obtained in both gas and liquid phase electrochemistry.

Claims

1. An immobilized electrochemical cell characterized in that the cell requires no self-contained electrolytic substance for ionization, the cell comprising:

a microelectrode having a cross-section diameter of less than about twenty-five (25) microns;

a reference electrode positioned less than about three (3) millimeters from the microelectrode; and

an insulative material positioned between the microelectrode and the reference electrode so as to maintain the electrodes a substantially fixed distance apart, the insulative material being dielectric but capable of ambient ion flow at the surface thereof for forming a charged layer of ions adjacent the microelectrode when a potential difference is applied between the microelectrode and the reference electrode, wherein a high magnitude electric field is created adjacent the microelectrode in the presence of minimal ambient ions, enabling electrochemical analysis in gaseous, liquid and solid environments.

2. An immobilized electrochemical cell characterized in that the cell requires no self-contained electrolytic substance for ionization, the cell comprising:

an insulative holder comprising a tube having an outer cross-sectional diameter of less than about six (6) millimeters, said tube having a tip;

a microelectrode sealed within the tube of the holder so as to extend to the tip, said microelectrode having a cross-sectional diameter of less than about twenty-five (25) microns; and

a reference electrode coating at least a portion of the tube of the holder so as to surround the microelectrode;

the tip of the tube of the insulative holder being formed of insulative material which is dielectric but capable of ambient ion flow at the surface thereof forming a charged layer of ions adjacent the microelectrode when a potential difference is applied between the microelectrode and the reference electrode, whereby a high magnitude electric field is created adjacent the microelectrode in the presence of minimal ambient ions, enabling electrochemical analysis in gaseous, liquid and solid environments.

3. An electrochemical sensor system, comprising:

an electrochemical cell characterized in that the cell requires no self-contained electrolytic substance for ionization, the cell comprising;

a microelectrode having a cross-sectional diameter of less than about twenty-five (25) microns;

a reference electrode positioned less than about three (3) millimeters from the microelectrode; and

an insulative material positioned between the microelectrode and the reference electrode so as to maintain the electrodes a substantially fixed distance apart, the insulative material being dielectric but capable of ambient ion flow at the surface thereof for forming a charged layer of ions adjacent the microelectrode when a potential difference is applied between the microelectrode and the reference electrode, whereby a high magnitude electric field is created adjacent the microelectrode in the presence of minimal ambient ions, enabling electrochemical analysis in gaseous, liquid and solid environments;

a potential source electrically connected to the microelectrode; and

means electrically connected to the reference electrode for detecting an electrical current between the microelectrode and the reference electrode.

4. A method for manufacturing an immobilized electrochemical cell which requires no self-contained electrolytic substance for ionization, the method comprising the steps of:

inserting a microelectrode having a cross-sectional diameter of less than about twenty-five (25) microns into an insulative holder which comprises a tube having an outer cross-sectional diameter of less than about six (6) millimeters and which is formed of an insulative material which is dielectric but capable of ambient ion flow at the surface thereof;

sealing the microelectrode within the tube of the insulative holder; and

coating the tube of the insulative holder with a conductive material so as to form a reference electrode surrounding the microelectrode,

the cell being operable for forming a charged layer of ions adjacent the microelectrode which a potential difference is applied between the microelectrode and the reference electrode, whereby a high magnitude electric field is created adjacent the microelectrode in the presence of minimal ambient ions, enabling electrochemical analysis in gaseous, liquid and sold environments