Fiber optic CO.sub.2 sensor

• US 4,943,364 A
• Filed: 06/23/1986
• Issued: 07/24/1990
• Est. Priority Date: 06/21/1985
• Status: Expired due to Term

• Current Assignee: Becton Dickinson Critical Care Systems Pte Ltd. (Becton, Dickinson & Co)
• Original Assignee: Spectramed, Inc.
• Inventors: Koch, Mark, Murray, Richard C. Jr.
• Primary Examiner(s): Schofer, Joseph L.
• Assistant Examiner(s): Lipman, Bernard
• Application Number:
  US06/877,572
• Time in Patent Office: 1,492 Days
• Field of Search: 204/415, 204/433
• US Class Current: 204/415
• CPC Class Codes: G01N 2021/6484 Optical fibres
• CPC Class Codes: G01N 2021/772 Tip coated light guide
• CPC Class Codes: G01N 2021/7786 Fluorescence
• CPC Class Codes: G01N 21/643 non-biological material
• CPC Class Codes: G01N 21/7703 using reagent-clad optical fibres or optical waveguides using measurement of total internal reflection or attenuated total reflection G01N21/552; optical fibres or waveguides per se G02B
• CPC Class Codes: G01N 21/80 Indicating pH value

Abstract

A fiber-optic probe for measuring the partial pressure of CO₂ in a medium includes a single optical fiber having a distal end; a mirror; a hydrolyzed dye/gel polymer, the dye being in contact with a bicarbonate solution; a solution permeable membrane covering the fiber distal end, hydrogel and mirror; and a gas-permeable membrane covering the solution permeable membrane.

Claims

1. A fiber-optic probe for measuring the partial pressure of carbon dioxide in a medium, comprising:

a gas-permeable membrane;

a hydrolyzed hydrogel including a dye/bicarbonate/gel acrylic or ethylene oxide polymer within the gas/permeable membrane, the hydrogel having been prepared from a chemically and optically unstable dye/gel acrylic or ethylene oxide polymer which, prior to treatment, contains weakly bonded dye molecules and exhibits a substantial drift in measured pH with time accompanied by an increase in protonation constant, by a treatment comprising (1) contacting the unstable polymer with a dilute aqueous base solution for a period of time sufficient to remove weakly bonded dye molecules from the polymer (2) washing the base-treated polymer with water to remove substantially all the base, (3) contacting the washed polymer with a solvent having a high affinity for water to remove water from the polymer and give a polymer characterized by chemical and optical stability with respect to dye loss with time and a consistently repeatable protonation constant, and (4) conditioning the stable polymer by contacting it with a bicarbonate solution;

means for providing light to the hydrolyzed hydrogel, and

means for transmitting absorbable light from the hydrolyzed hydrogel.

2. A fiber-optic probe as recited in claim 1 wherein the gel polymer is selected from the group consisting of polyacrylamides and polyethylene oxides.

3. A fiber-optic probe as recited in claim 2 wherein the gel polymer is a polyacrylamide.

4. A fiber-optic probe as recited in claim 1 wherein the dye is selected from the group consisting of phenol red, cresol red, neutral red and bromothymol blue.

5. A fiber-optic probe as recited in claim 4 wherein the gel polymer is a polyacrylamide.

6. A fiber-optic probe as recited in claim 1 further comprising a solution-permeable membrane interposed between the gas-permeable membrane and the hydrolyzed hydrogel.

7. A fiber-optic probe as recited in claim 6 wherein the solution-permeable membrane is a hollow fiber membrane selected from the group consisting of porous polyethylenes, porous polypropylenes, porous polytetrafluorethylene and dialysis tubing.

8. A fiber-optic probe as recited in claim 7 wherein the gas-permeable membrane is coated on the exterior of the hollow-fiber membrane and is selected from the group consisting of silicone rubbers, latex rubbers and polyurethanes.

9. A fiber-optic probe as recited in any one of claims 1-8, inclusive, wherein the means for providing light to the hydrolyzed hydrogel comprises an optical fiber having a distal end located within the gas-permeable membrane and the means for transmitting absorbable light from the hydrolyzed hydrogel comprises a mirror located within the gas-permeable membrane, the hydrogel being interposed between the distal end of the optical fiber and the mirror.