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Ion exchange membranes and dissolved gas sensors

a technology of dissolved gas and ion exchange membrane, which is applied in the direction of steering control, liquid/fluent solid measurement, instruments, etc., can solve the problems of increasing the complexity of the sensor, limiting the lifetime of the sensor, and inherently prone to instability and limited lifetime of the clark cell

Inactive Publication Date: 2005-04-07
SENSIFIC TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

"The patent describes gas-permeable membranes that can selectively permeable gases and have the ability to remove ionic products from a redox reaction used to detect the gas. These membranes can also replenish electrolyte components and alleviate problems associated with sensor exhaustion. This allows for the construction of small and long-lasting stable sensors."

Problems solved by technology

The stability and reliability of Clark cells depends on many factors, but in particular there is a limitation on sensor lifetime imposed by the amount of electrolyte within the Clark cell.
Since oxidation and reduction processes consume components of the electrolyte, Clark cells are inherently prone to instability and limited lifetime due to exhaustion of the electrolyte.
Mechanical solutions, however, tend to increase the complexity of the sensor (see, for example, European Patent No.
For these reasons, Clark cells are typically expensive to construct and require frequent maintenance and calibration.

Method used

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  • Ion exchange membranes and dissolved gas sensors
  • Ion exchange membranes and dissolved gas sensors
  • Ion exchange membranes and dissolved gas sensors

Examples

Experimental program
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Effect test

example 1

Amperometric Sensors With a Solid Electrolyte Salt

The membranes described herein may be used to construct a sensor with a solid electrolyte. Such sensors may be constructed as follows: 1) An anode and cathode are placed upon a gas-impervious, electrically insulating substrate using standard printed circuit board techniques (see, for example, U.S. Pat. No. 4,534,356). In some embodiments a third electrode or “guard ring” also may be formed on the substrate in the same manner as the other electrodes. For example, the electrodes may be formed using an appropriate mask (e.g. photoresist) and metal slurries (e.g. metal slurries provided by Englehard, E. I. duPont de Nemours, or Johnson Matthey). If one of the electrodes is to be a silver / silver halide electrode it may be formed by depositing silver on the surface of the substrate and then halogenating the silver electrode by electrochemical techniques. For example, the silver electrode may be halogenated by chloridation using a soluti...

example 2

Characterization of a Gas-Permeable Membrane Containing an Ion Exchanger

This example demonstrates the ion-exchange capacity of the disclosed membranes and its implications for making stable, low-volume dissolved oxygen (DO) electrodes. The advantage of the DO electrode is best seen under “forcing” conditions in which electrode failure occurs in a relatively brief period (<24 hours). This can be achieved using a limited amount of electrolyte: an electrode producing a 0.2 μA current will consume the available chloride ions in 3 μL of 0.01 M NaCl in about 4 hours.

A PVC / dioctyl adipate membrane comprising tetradecylguanidinium chloride was tested with an experimental system that uses a measurement volume of 0.35M NaCl at 12±0.5° C. and a set potential of 0.500±0.001V. The system was stirred from below and the solutions were open to the atmosphere, so daily pressure variations could be seen in the longer data records. The probe uses a Pt cathode (˜0.5 mm diameter) at the center ...

example 3

Construction and Characterization of a Printed Circuit Board Dissolved Oxygen Sensor

The components of a printed circuit board (PCB) sensor constructed using the techniques described in Example 1 is shown in FIG. 7. FIG. 7 shows a cross-section of sensor (10) that includes substrate (20), cathode (30), such as a gold cathode, an anode (40), such as a silver / silver chloride reversible anode, optional guard ring (50), such as a silver guard ring, solid electrolyte (e.g. NaCl) layer (60), and gas-permeable membrane (70), such as a PVC / dioctyl adipate membrane comprising tetradecylguanidinium chloride as the anion exchanger. FIG. 8 shows a top view of a PCB dissolved oxygen sensor (without the optional guard ring) having a gold cathode (100), silver / silver chloride reversible anode (110), and electrical contacts (120).

Briefly, the printed circuit board (PCB) sensor was produced from computer Gerber plots using gold plated traces and pads. The PCB sensor was also selectively plated wi...

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Abstract

Ion exchange membranes for use in sensors that measure dissolved gases are described. Sensors constructed using the disclosed membranes are able to maintain electrolyte conditions within the electrolyte volume so as to have greatly extended and more stable lifetimes than sensors of similar construction and electrolyte volume constructed with standard membranes.

Description

FIELD The invention relates to ion exchange membranes and dissolved gas sensors. BACKGROUND Measurement of dissolved gases is important in many fields, including medicine, food science and environmental science. One type of sensor developed to measure dissolved gases is the Clark cell. Clark cells are used to detect gases that are readily reduced or oxidized, such as hydrogen sulfide, NO, NO2, CO, Cl2 and O2. These sensors consist of a gas permeable membrane enclosing an electrolyte and working and reference electrodes in contact with the electrolyte (see, for example, Janata, J., Principles of Chemical Sensors, Plenum Publishing, 1991 and Polarographic Oxygen Sensors, Chapter 4, Gnaiger, E. and Forstner, H. (Eds.), Springer-Verlag, 1983). Gases pass through the membrane by diffusion, and are reduced or oxidized at the working electrode to create a detectable current flow. The stability and reliability of Clark cells depends on many factors, but in particular there is a limitatio...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B01D53/22B62D1/06B62D1/14B62J33/00B62K21/26G01N27/49G05D23/19
CPCB01D53/228B62D1/065B62D1/14G05D23/1909B62K21/26G01N27/404B62J33/00
Inventor FYLES, THOMAS MURRAYROBERTSON, GEORGE DAVIDROWE, ROBERT DONALD
Owner SENSIFIC TECH