POLAROGRAPHIC SENSOR AND MEMBRANE THEREFOR

• US 3,718,563 A
• Filed: 02/22/1971
• Issued: 02/27/1973
• Est. Priority Date: 02/22/1971
• Status: Expired due to Term

• Current Assignee: Donald N. Martin, Irwin H. Krull
• Original Assignee: Donald N. Martin, Irwin H. Krull
• Inventors: Krull, Irwin H., Martin, Donald N.
• Primary Examiner(s): Kaplan, G. L.
• Application Number:
  US05/117,633
• Time in Patent Office: 736 Days
• Field of Search: 204/195P,1T 324/29
• US Class Current: 204/415
• CPC Class Codes: G01N 27/404 Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid , e.g. Clark-type oxygen sensors

Abstract

A polarographic sensor comprising a pair of electrodes joined by an electrolyte with a multi-layer gas permeable-essentially ion impermeable membrane separating the electrodes and electrolyte from the sample medium. The layers of the membrane are held together so as to prevent migration of electrolyte therebetween to the region overlying the sensing electrode and to prevent the trapping of gas or liquid between the layers in such region. The outer layer of the membrane is preferably formed of silicone rubber while the next layer is formed of a material which is less permeable to gas and water vapor than the outer membrane, for example Teflon. A polarographic sensor employing such a membrane exhibits good time response and minimal flow sensitivity.

Claims

2. A sensor as set forth in claim 1 wherein:

said inner layer is selected from the group consisting of polyethylene, polypropylene and a polymer of a fluorinated alkane.

3. A sensor as set forth in claim 1 wherein:

said inner layer is either polytetrafluoroethylene or fluorinated ethylene propylene.

4. A sensor as set forth in claim 1 wherein:

the thickness of said outer layer is less than the product of the thickness of said inner layer and 20.

5. A sensor as set forth in claim 4 wherein:

the thickness of said inner layer is less than about 2 mils.

6. A sensor as set forth in claim 3 wherein:

the thickness of said inner layer is between about 0.5 and 1 mils; and

the thickness of said outer layer is between about 3 and 6 mils.

7. A sensor as set forth in claim 1 wherein:

said sensing electrode is composed of a plurality of spaced wires imbedded in an insulating element and exposed at one end adjacent to said membrane.

8. A sensor as set forth in claim 1 wherein:

said holding means comprises means bonding said layers together at their mating surfaces to provide a composite multilayer membrane sandwich.

9. A sensor as set forth in claim 1 wherein:

said inner and outer layers are separate sheets;

said sensor including a body having a cavity therein receiving said electrodes and adapted to hold said electrolyte;

said inner layer being positioned to close said cavity;

said holding means clamping said outer layer under tension over said inner layer to hold inner layer against said body in sealing engagement therewith; and

the outer periphery of said inner layer being disposed inside said holding means so that air may escape from between said layers when said layers are mounted onto said body by said holding means.