Acidic gas sensors and method of using same
First Claim
1. An electrochemical sensor for sensing the amount of an acidic gas in a fluid, the sensor comprising a sensing electrode, a counter electrode and an intervening body of electrolyte that is accessible to the gas being tested, the electrolyte containing a complex of a metal having at least one ligand selected from the group consisting of propane diamine and ethylene diamine that can be displaced by the presence in the electrolyte of an acidic gas to form a modified complex in which the metal has the same oxidation state as in the unmodified complex, the system being such that the modified complex is electrochemically detectable at the sensing electrode at a potential at which the unmodified complex is electrochemically unreactive and which is above the potential at which oxygen is electrochemically reduced.
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Abstract
The present invention provides a sensor, preferably an electrochemical sensor, for detecting acidic gases, e.g. carbon dioxide. The electrochemical sensor has a sensing electrode (20, 22), a counter electrode (37) and a body of electrolyte containing a complex, e.g. copper(II) bis(propanediamine), which has one or more ligands that is displaceable by the presence of the acidic gas in the electrolyte to form a modified complex which can be electrochemically reacted at the sensing electrode at a potential at which the unmodified complex is unreactive. The acidic gas diffuses into the electrolyte through a porous membrane. The modified complex can also be detected colorimetrically because it absorbs light at a different wavelength to the unmodified complex.
73 Citations
17 Claims
- 1. An electrochemical sensor for sensing the amount of an acidic gas in a fluid, the sensor comprising a sensing electrode, a counter electrode and an intervening body of electrolyte that is accessible to the gas being tested, the electrolyte containing a complex of a metal having at least one ligand selected from the group consisting of propane diamine and ethylene diamine that can be displaced by the presence in the electrolyte of an acidic gas to form a modified complex in which the metal has the same oxidation state as in the unmodified complex, the system being such that the modified complex is electrochemically detectable at the sensing electrode at a potential at which the unmodified complex is electrochemically unreactive and which is above the potential at which oxygen is electrochemically reduced.
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9. A sensor for sensing carbon dioxide in a fluid, which sensor comprises:
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a body accessible to carbon dioxide in the fluid, and containing a copper (II) complex having at least one amine ligand(s), the ligand(s) being reversibly displaceable from the copper atom in the presence of carbon dioxide to form a modified copper complex in which the metal has the same oxidation state as in the unmodified complex; and means for detecting the increase in the concentration of said modified copper complex and/or the decrease in the concentration of said copper-amine complex and for providing a signal in accordance with the concentration of complex detected. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method of sensing the amount of carbon dioxide in a fluid, the method comprising contacting the fluid with a body containing a copper (II) complex having at least one amine ligand that, in the presence of carbon dioxide, is reversibly displaceable from the copper atom to form a modified copper complex in which the metal has the same oxidation state as in the unmodified complex, and measuring the amount of the modified complex and/or the amount of the copper amine complex in the body to provide an indication of the amount of carbon dioxide in the fluid.
Specification