Enzymatic toxic gas sensor

Claim 2

A enzymatic toxic gas sensor wherein the chemical reactions therein are activated by diffusion within the sensor, said sensor comprising: a reservoir containing a buffered electrolyte; a wick attached at one end thereof to said reservoir; a porous membrane having one broadside adapted for interfacing with the ambient air; a structure attached to the other broadside of said membrane, said structure having an enzyme covalently attached thereto; an electrochemical cell means having a sensing electrode, a reference electrode and a counter electrode; said sensing electrode spaced from said structure and adapted to react with reaction products of said enzyme to generate an electrical current; substrate means adapted to receive the other end of said wick and containing a substrate which is dissolvable by said buffered electrolyte and diffuses to said enzyme to react with said enzyme in the absence of toxic gases; and circuit means responsive to said electrochemical cell to generate a signal of one value due to the presence of toxic gases for activating an alarm means and a signal of another value due to the absence of toxic gases.

Claim 3

A sensor according to claim 1 additionally including: separator means interposing said reservoir and said substrate means to prevent a reaction therebetween; and a pin actuation means operatively connected to said separator means for removing said separator means when said pin is removed from the sensor.

Claim 4

A gas sensor according to claim 1 wherein said structure contains acetylcholinesterase (AcHe) covalently coupled to glass beads attached to the other broadside of said membrane.

Claim 5

A gas sensor according to claim 3 wherein said alarm means is responsive to the deactivation of said acetylcholinesterase by means of a toxic gas.

Claim 6

The apparatus of claim 1 wherein said enzyme includes yeast alcohol dehydrogenase.

Claim 7

A gas sensor according to claim 1 wherein said alarm means is responsive to the deactivation of said enzyme by means of a toxic gas.

Claim 8

A dual enzymatic toxic gas sensor wherein the chemical reactions therein are activated by diffusion within the sensor, said sensor comprising: a first sensor having: a reservoir containing a buffered electrolyte; a wick attached at one end thereof to said reservoir; a porous membrane having one broadside adapted for interfacing with the ambient air; a structure attached to the other broadside of said membrane, said structure having an enzyme covalently attached thereto; an electrochemical cell means having a sensing electrode, a reference electrode and a counter electrode; said sensing electrode spaced from said structure and adapted to react with reaction products of said enzyme to generate an electrical current; substrate means adapted to receive the other end of said wick and containing a substrate which is dissolvable by said buffered electrolyte and diffuses to said enzyme to react with said enzyme in the absence of toxic gases; a second sensor having: a reservoir containing a buffered electrolyte; a wick attached at one end thereof to said reservoir; a porous membrane having one broadside adapted for interfacing with the ambient air; removable cover means normally covering said one broadside from interfacing with ambient air and adaptable to be removed therefrom; a structure attached to the other broadside of said membrane, said structure having an enzyme covalently attached thereto; an electrochemical cell means having a sensing electrode, a reference electrode and a counting electrode; said sensing electrode spaced from said structure and adapted to react with reaction products of said enzyme to generate an electrical current; substrate means adapted to receive the other end of said wick and containing a substrate which is dissolvable by said buffered electrolyte and diffuses to said enzyme to react with said enzyme in the absence of toxic gases; and circuit means including a bridge circuit, summing means and alarm means responsive to each of said electrochemical cells from said first and second sensors to generate a signal of one value due to the presence of toxic gases and a signal of another value due to the absence of toxic gases for activating said alarm means and responsive to the removal of said cover means to generate one of said signals in response to the electrical current from said electrochemical cell in said second sensor.

Claim 9

A dual enzymatic toxic gas sensor wherein the chemical reactions therein are activated by diffusion within the sensor, said sensor comprising: a first sensor having: a reservoir containing a buffered electrolyte; a wick attached at one end thereof to said reservoir; a porous membrane having one broadside adapted for interfacing with the ambient air; a structure attached to the other broadside of said membrane, said structure having an enzyme covalently attached thereto; an electrochemical cell means having a sensing electrode, a reference electrode and a counter electrode; said sensing electrode spaced from said structure and adapted to react with reaction products of said enzyme to generate an electrical current; substrate means adapted to receive the other end of said wick and containing a substrate which is dissolvable by said buffered electrolyte and diffuses to said enzyme to react with said enzyme in the absence of toxic gases; a second sensor having: a reservoir containing a buffered electrolyte; a wick attached at one end thereof to said reservoir; a porous membrane having one broadside adapted for interfacing with the ambient air; removable cover means normally covering said one broadside from interfacing with ambient air and adaptable to be removed therefrom; a structure attached to the other broadside of said membrane, said structure having an enzyme covalently attached thereto; an electrochemical cell means having a sensing electrode, a reference electrode and a counting electrode; said sensing electrode spaced from said structure and adapted to react with reaction products of said enzyme to generate an electrical current; substrate means adapted to receive the other end of said wick and containing a substrate which is dissolvable by said buffered electrolyte and diffuses to said enzyme to react with said enzyme in the absence of toxic gases; and circuit means including a bridge circuit, summing means and alarm means responsive to each of said electrochemical cells from said first and second sensors to generate a signal of one value due to the presence of toxic gases and a signal of another value due to the absence of toxic gases for activating said alarm means and responsive to the removal of said cover means to generate one of said signals in response to the electrical current from said electrochemical cell in said second sensor.

Claim 10

A sensor according to claim 7 additionally including: separator means interposing each of said reservoir and said substrate means to prevent a reaction therebetween; and a pin actuation means operatively connected to each of said separator means for removing said separator means when said pin is removed from the sensor.

Claim 11

A gas sensor according to claim 7 wherein each of said structures contains acetylcholinesterase (AcHe) covalently coupled to glass beads attached to the other broadside of said membrane.

Claim 12

A gas sensor according to claim 9 wherein said alarm means is reponsive to the deactivation of said acetylcholinesterase by means of a toxic gas.

Claim 13

Apparatus for detecting certain toxic gases in an ambient gas comprising: a substrate, a pouch enclosing said substrate, a pouch solvent positioned in said pouch for dissolving said substrate, said pouch including a porous membrane in a wall of said pouch, said pouch solvent and dissolved substrate positioned in contact with said porous membrane to permit said dissolved substrate to diffuse through said porous membrane, a buffered electrolyte positioned in contact with said porous membrane, whereby said substrate diffusing through said porous membrane dissolves into said electrolyte, an immobilized enzyme in contact with said buffered electrolyte to catalyze a reaction with said dissolved substrate to form reaction products, means for dissolving said toxic gases from an ambient gas into said electrolyte to permit them to inhibit said enzyme, an electrochemical cell means having a sensing electrode, a reference electrode and a counter electrode; said sensing electrode spaced from said immobilized enzyme and adapted to react with reaction products of said substrate catalyzed by said enzyme to generate an electrical current; circuit means coupled to said electrochemical cell to generate a signal indicative at first times of an ongoing catalyzed reaction and at second times of a diminished catalyzed reaction due to an inhibited enzyme.

Claim 14

Apparatus for detecting certain toxic gases in an ambient gas comprising: a substrate, a pouch enclosing said substrate, a pouch solvent positioned in said pouch for dissolving said substrate, said pouch including a porous membrane in a wall of said pouch, said pouch solvent and dissolved substrate positioned in contact with said porous membrane to permit said dissolved substrate to diffuse through said porous membrane, a buffered electrolyte positioned in contact with said porous membrane, whereby said substrate diffusing through said porous membrane dissolves into said electrolyte, an immobilized enzyme in contact with said buffered electrolyte to catalyze a reaction with said dissolved substrate to form reaction products, means for dissolving said toxic gases from an ambient gas into said electrolyte to permit them to inhibit said enzyme, an electrochemical cell means having a sensing electrode, a reference electrode and a counter electrode; said sensing electrode spaced from said immobilized enzyme and adapted to react with reaction products of said substrate catalyzed by said enzyme to generate an electrical current; circuit means coupled to said electrochemical cell to generate a signal indicative at first times of an ongoing catalyzed reaction and at second times of a diminished catalyzed reaction due to an inhibited enzyme.

Claim 15

The apparatus of claim 11 wherein said porous membrane includes polypropylene.

Claim 16

The apparatus of claim 11 wherein said porous membrane includes PTFE (polytetrafluoroethylene).

Claim 17

The apparatus of claim 11 wherein said buffered electrolyte includes tris-(hydroxymethyl) aminomethane.

Claim 18

The apparatus of claim 11 further including filter paper to position said buffered electrolyte.

Claim 19

The apparatus of claim 11 wherein said substrate includes acetylthiocholine perchlorate.

Claim 20

The apparatus of claim 11 wherein said porous membrane passes by diffusion approximately 2.0×10 -8 moles per minute of said substrate.

Claim 21

The apparatus of claim 11 wherein said enzyme includes cholinesterase.

Claim 22

The apparatus of claim 11, wherein said enzyme includes yeast alcohol dehydrogenase.