GB2290617A - Water quality measuring apparatus - Google Patents
Water quality measuring apparatus Download PDFInfo
- Publication number
- GB2290617A GB2290617A GB9415711A GB9415711A GB2290617A GB 2290617 A GB2290617 A GB 2290617A GB 9415711 A GB9415711 A GB 9415711A GB 9415711 A GB9415711 A GB 9415711A GB 2290617 A GB2290617 A GB 2290617A
- Authority
- GB
- United Kingdom
- Prior art keywords
- electrodes
- electrode
- pair
- water
- measurement
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 19
- 238000005259 measurement Methods 0.000 claims abstract description 25
- 239000000460 chlorine Substances 0.000 claims abstract description 17
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 16
- 229910052801 chlorine Inorganic materials 0.000 claims abstract description 16
- 239000000758 substrate Substances 0.000 claims abstract description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 5
- 229910000510 noble metal Inorganic materials 0.000 claims abstract description 5
- 239000000919 ceramic Substances 0.000 claims abstract description 4
- 239000011263 electroactive material Substances 0.000 claims abstract description 4
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 abstract description 3
- 239000004033 plastic Substances 0.000 abstract description 2
- 229920003023 plastic Polymers 0.000 abstract description 2
- 238000004140 cleaning Methods 0.000 abstract 1
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 8
- 239000000463 material Substances 0.000 description 4
- 229910052697 platinum Inorganic materials 0.000 description 4
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 3
- 229910052737 gold Inorganic materials 0.000 description 3
- 239000010931 gold Substances 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 229910052709 silver Inorganic materials 0.000 description 3
- 239000004332 silver Substances 0.000 description 3
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- -1 silver halide Chemical class 0.000 description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 238000003149 assay kit Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 239000003651 drinking water Substances 0.000 description 1
- 235000020188 drinking water Nutrition 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000010408 film Substances 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 238000004659 sterilization and disinfection Methods 0.000 description 1
- 230000009182 swimming Effects 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/403—Cells and electrode assemblies
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/18—Water
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/18—Water
- G01N33/182—Specific anions in water
Landscapes
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Pathology (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Physics & Mathematics (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Food Science & Technology (AREA)
- Medicinal Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Molecular Biology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
Abstract
A sensor device for the measurement of electro-active material in water e.g Cl, comprises insulative substrate 1 e.g. of ceramic, carrying interdigitated electrodes 2, 3, a pair of electrodes 4, 5, a reference electrode 6 and conductive pads 8 - 12 to connect the device to electrical measurement apparatus. The reference electrode 6 may be partly surrounded by a screen 7. Electrodes 2, 3 are preferably microelectrodes and the conductive regions may be of noble metal or carbon. The device may be submersible for one off measurements or have water flow across it continuously. The device may be incorporated in a capillary-fill plastics vessel where the substrate forms the bottom plate of the vessel and the top plate is fixed for single use or removable for cleaning. In use, a potential applied between electrodes 3 and 5 produces a current related to chlorine concentration, and a potential applied between electrode 2 and generator electrode 4 controls pH in the region of working electrode 3. The apparatus may also be used to measure ozone. <IMAGE>
Description
WATER QUALITY MEASURING APPARATUS
This invention relates to water quality measuring apparatus and more especially it relates to apparatus for measurement of electro-active material such as ozone or chlorine in water.
The measurement of chlorine levels in drinking water is an important need so that the level required for disinfection can be maintained within predetermined limits. There is also a requirement to monitor chlorine in swimming pools. These tests or measurements are done at present by measuring the redox potential which is an uncertain and insensitive method, or alternatively, by the use of inconvenient and inaccurate test kits.
Micro-electrodes have been used in known arrangements to measure chlorine in water with the advantage that because of the
small size of the electrodes the effects of water turbulence, as may
occur during continuous flow measurements, are minimised.
However, micro-electrodes of the kind used in the known
arrangements use very small currents which produce poor signal
to noise ratios, and moreover are difficult to fabricate in a
repeatable manner.
It is an object of the present invention to provide a simple
robust system for the measurement of chlorine which can be the
basis of continuous or single use measurements, and which
provides good signal to noise ratios in use.
According to the present invention we provide for the
measurement of electro-active material (such as chlorine) in
water, a sensor device which in use is exposed to water to be tested, which sensor device comprises an insulative substrate arranged to support conductive regions which define, a first pair of electrodes each having a plurality of mutually spaced fingers, wherein the fingers of one electrode are interdigitated with and spaced apart from the fingers of the other electrode, and a second pair of electrodes, and conductive pads electrically connected to each of the said electrodes, which pads serve to facilitate connection of the device to electrical measurement apparatus, and operatively associated with the device a reference electrode.
The reference electrode may be supported on the insulative substrate and defined by a part of the conductive regions.
The pairs of electrodes may be micro-electrodes.
The term micro-electrode when used herein is intended to cover electrodes of very small width, eg. about 25 Rm or less, the length being about 20 times larger than the width, or more within reasonable limits.
In use of the device a potential referenced to the reference electrode is applied between a working electrode, which is defined by one of the first pair of electrodes, and a counter electrode which is defined by one of the second pair of electrodes, to produce a current in dependence upon which chlorine concentration in the water is indicated. a further potential being applied between a generator electrode. defined by the other of the said first pair of electrodes and a generator counter electrode, defined by the other of the said second pair of electrodes, which further potential serves to control pH in the region of the working electrode, whereby consistent and repeatable measurement is facilitated. This controlled pH may be acid or alkaline, dependent upon the relative polarity of the generator electrodes.Thus, if the generator electrode is positive with reference to the counter generator electrode there will be an acidic environment around the generator electrode and of course vis-versa.
An important feature of the present invention is the use of a working electrode and a generator electrode having interdigitated fingers which effectively serve to provide an extended path through which measurement is made. This feature provides for relatively large operating currents and consequently greatly increased sensitivity and much better signal to noise performance when micro-electrodes are used. The provision of a device is thereby facilitated which may be simply fabricated using conventional thick film techniques, or thin film techniques using sputtering for example, and which will in use afford consistently repeatable performance.
The conductive regions may conveniently all be made of a noble metal such as palladium, platinum, or gold or alternatively they may be made of carbon or any combination of these materials.
In a case when the conductive region are all made of a noble metal or carbon or any combination of these materials, the reference electrode may comprise a region of the conductive material supported on the substrate and surrounded at least in part by an H+ or an OH- generating structure.
Alternatively, the reference electrode may comprise silver, or a silver halide/silver halide dielectric structure and the other electrodes may comprise platinum, gold or carbon.
In this latter arrangement, the conductive pads may also be made of platinum or alternatively they may be made from any other suitable conductive material, which may be plated to improve wear resistance and/or to minimise electrical contact resistance, with material such as gold or paladium for example.
The insulative substrate may be made of ceramic.
The reference electrode is preferably at least partly surrounded in spaced apart relationship by a screen which is supported on the substrate and connected electrically to the generator electrode.
The device may be operatively associated with measurement apparatus which provides the necessary electrical voltages and which provides an indication of chlorine level in dependence upon current flowing between the working electrode and its associated counter electrode working a potentiostatic or in a voltammetric mode.
One embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which;
Figure 1 is a generally schematic plan view (not to scale) of a chlorine measurement device and
FIGURE 2 is a graph showing variation of the output of the device shown in Figure 1 with variation of chlorine concentration in water.
Referring now to the drawings, a chlorine measurement device comprises a substrate 1 made of ceramic on which are supported conductive tracks defining a pair of first electrodes 2 and 3, a pair of second electrodes 4 and 5, a reference electrode 6 and a pH generating structure 7 made of a noble metal such as platinum. As can be seen from the drawing, the pair of first electrodes, each comprise a comb like structure comprising a plurality of fingers wherein the fingers of one electrode are interdigitated symmetrically with the fingers of the other electrode. The number of fingers used may be varied according to the application but it is envisaged that up to 150 fingers may be provided on each electrode.
In use of the device as shown in the drawing, the electrodes 2 and 3 of the first pair, which are interdigitated micro-electrodes, are used respectively to define a generator electrode and a working electrode. In the present example, fingers of each electrode are 20 Rm wide and are spaced apart from the adjacent fingers of the other electrode of the pair by 20 plum. The electrodes 4 and 5 of the second pair are used on the other hand to define counter electrodes, the electrode 4 being used as a generator counter electrode, and the electrode 5 being used as a working counter electrode. In order to apply appropriate potentials to the electrodes 2, 3, 4, 5 and 6, connection pads 8, 9, 10, 11 and 12 respectively are provided. In use of the device a voltage of about -.1 volt is applied via the pad 10 to the working electrode 3 which might be described as a potentiostatic mode of operation.
Alternatively, in a voltammetric mode of operation, a potential ramp would be applied having a start potential +.5 volts and an end potential of -.5 volts, the peak current being measured. At the same time, a voltage of about -2 volts is applied to the generator electrode 2 via the pad 9. The voltages are referenced to the corresponding counter electrodes 4 and 5 and the reference electrode which are maintained at substantially zero voltage.
Chlorine concentration is indicated by means of apparatus (not shown) in dependence upon the current which flows between the working electrode 3 and its associated working counter electrode 5. The negative voltage applied between the generator electrode 2 and its associated generator counter electrode 4 is used to provide in the region of the electrodes, a controlled pH environment to facilitate consistent and accurate measurements.
In operation of the device as shown in Figure 1, variation of the output with variation in chlorine concentration, is as shown in
Figure 2. It will be appreciated that conductive parts not taking part in measurements, such as submerged exposed tracks, will be insulated by means of a suitable insulative coating.
The device shown may be arranged to form a part of a submersible cell for one off measurements, or alternatively it may form a part of a measuring system wherein water is arranged continuously to flow across the electrodes to provide for continuous read outs.
A particularly convenient format for single use operation is provided by making the substrate as the bottom plate of a capillary fill device, the top plate. forming a thin layer sample cell, which may be manufactured of a plastics material formed by injection moulding incorporating a 100 Rm step to provide the capillary gap. In operation of the capillary fill device, water to be tested is drawn between the plates by capillary attraction so that electrodes, as shown in Figure 1 of the accompanying drawings, which are carried on the bottom plate, are exposed to water to be tested. The device may be a 'single use device' which is normally thrown away after a measurement has been made or alternatively re-use may be arranged by providing a removable top plate so that the cell may be suitably cleared to facilitate re-use.
As will be apparent to those skilled in the art, with appropriate changes in the operating potential, a device as just before described may be used for the measurement of other electro-chemically oxidised or reduced species in water, such as ozone for example.
Claims (10)
1. For the measurement of electro-active material in water, a sensor device which in use is exposed to water to be tested, which sensor device comprises an insulative substrate arranged to support conductive regions which define, a first pair of electrodes each having a plurality of mutually spaced fingers, wherein the fingers of one electrode are interdigitated with and spaced apart from the fingers of the other electrode, and a second pair of electrodes, and conductive pads electrically connected to each of the said electrodes, which pads serve to facilitate connection of the device to electrical measurement apparatus and operatively associated with the device a reference electrode.
2. A sensor device as claimed in Claim 1, wherein the reference electrode is supported on the insulative substrate and defined by a part of the conductive regions.
3. A sensor device as claimed in Claim 2, wherein the reference electrode is at least partly surrounded by a H+ or a OH- generating structure.
4. A device as claimed in any preceding claim, wherein the first pair of electrodes are micro-electrodes.
5. A device as claimed in any preceding claim, wherein the conductive regions comprise a noble metal.
6. A device as claimed in any of Claims 1 to 4, wherein the conductive regions comprise carbon.
7. A device as claimed in any preceding claim, wherein the insulative substrate is made of ceramic.
8. A device as claimed in any preceding claim, operatively associated with measurement apparatus which provides the necessary electrical voltages and which provides an indication of chlorine level in dependence upon current flowing between the working electrode and its associated counter electrode.
9. A device as claimed in any preceding claim and substantially as hereinbefore described with reference to the accompanying drawings.
10. Apparatus including a device as claimed in any preceding claim, which in use provides a potential referenced to the reference electrode which is applied between a working electrode, which is defined by one of the first pair of electrodes, and a working counter electrode which is defined by one of the second pair of electrodes, to produce a current in dependence upon which chlorine concentration in the water is indicated, a further potential being applied between a generator electrode, defined by the other of the said first pair of electrodes, and a generator counter electrode, defined by the other of the said second pair of electrodes, which further potential serves to control pH in the region of the working electrode, whereby consistent and repeatable measurement is facilitated.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9412820A GB9412820D0 (en) | 1994-06-25 | 1994-06-25 | Water quality measuring apparatus |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9415711D0 GB9415711D0 (en) | 1994-09-21 |
| GB2290617A true GB2290617A (en) | 1996-01-03 |
| GB2290617B GB2290617B (en) | 1998-12-23 |
Family
ID=10757353
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9412820A Pending GB9412820D0 (en) | 1994-06-25 | 1994-06-25 | Water quality measuring apparatus |
| GB9415711A Expired - Fee Related GB2290617B (en) | 1994-06-25 | 1994-08-03 | Water quality measuring apparatus |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9412820A Pending GB9412820D0 (en) | 1994-06-25 | 1994-06-25 | Water quality measuring apparatus |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB9412820D0 (en) |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0973028A2 (en) * | 1998-07-14 | 2000-01-19 | Oxley Developments Company Limited | Electrode array |
| WO2002095387A1 (en) | 2001-05-22 | 2002-11-28 | Csem Centre Suisse D'electronique Et De Microtechnique Sa | Electrode system for electrochemical sensor |
| US6523426B1 (en) * | 1998-03-11 | 2003-02-25 | Siemens Plc | Water quality measuring apparatus with a sensing wafer clamped between two o-rings |
| US6740225B2 (en) * | 2000-03-07 | 2004-05-25 | Hathaway Brown School | Method for determining the amount of chlorine and bromine in water |
| EP1715334A1 (en) * | 2005-04-22 | 2006-10-25 | Adamant Technologies SA | Procedure utilising an electrochemical sensor and electrodes forming the sensor |
| US7189314B1 (en) * | 2002-09-06 | 2007-03-13 | Sensicore, Inc. | Method and apparatus for quantitative analysis |
| US7201831B2 (en) | 2002-02-22 | 2007-04-10 | Water Security And Technology, Inc. | Impurity detection device |
| EP1977226A1 (en) * | 2006-01-27 | 2008-10-08 | Intellitect Water Limited | An interdigitated microelectrode and a process for producing the interdigitated microelectrode |
| US8016991B2 (en) * | 2003-04-22 | 2011-09-13 | Robert Bosch Gmbh | Potentiometric sensor device |
| US20160319522A1 (en) * | 2013-12-20 | 2016-11-03 | Orbital Systems Ab | A water hybrid device |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0299780A2 (en) * | 1987-07-15 | 1989-01-18 | Sri International | Surface type microelectronic gas and vapor sensor |
| GB2229005A (en) * | 1989-03-10 | 1990-09-12 | Plessey Co Plc | Biosensor device |
| EP0569908A2 (en) * | 1992-05-11 | 1993-11-18 | Nippon Telegraph And Telephone Corporation | Electrochemical detection method and apparatus therefor |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5120421A (en) * | 1990-08-31 | 1992-06-09 | The United States Of America As Represented By The United States Department Of Energy | Electrochemical sensor/detector system and method |
-
1994
- 1994-06-25 GB GB9412820A patent/GB9412820D0/en active Pending
- 1994-08-03 GB GB9415711A patent/GB2290617B/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0299780A2 (en) * | 1987-07-15 | 1989-01-18 | Sri International | Surface type microelectronic gas and vapor sensor |
| GB2229005A (en) * | 1989-03-10 | 1990-09-12 | Plessey Co Plc | Biosensor device |
| EP0569908A2 (en) * | 1992-05-11 | 1993-11-18 | Nippon Telegraph And Telephone Corporation | Electrochemical detection method and apparatus therefor |
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6523426B1 (en) * | 1998-03-11 | 2003-02-25 | Siemens Plc | Water quality measuring apparatus with a sensing wafer clamped between two o-rings |
| EP0973028A3 (en) * | 1998-07-14 | 2001-01-03 | Oxley Developments Company Limited | Electrode array |
| EP0973028A2 (en) * | 1998-07-14 | 2000-01-19 | Oxley Developments Company Limited | Electrode array |
| US6740225B2 (en) * | 2000-03-07 | 2004-05-25 | Hathaway Brown School | Method for determining the amount of chlorine and bromine in water |
| WO2002095387A1 (en) | 2001-05-22 | 2002-11-28 | Csem Centre Suisse D'electronique Et De Microtechnique Sa | Electrode system for electrochemical sensor |
| US7270736B2 (en) | 2001-05-22 | 2007-09-18 | Adamant Technologies Sa | Electrode system for electrochemical sensor |
| US8080142B2 (en) | 2002-02-22 | 2011-12-20 | Water Security And Technology, Inc. | Impurity detection device and method |
| US8900429B2 (en) | 2002-02-22 | 2014-12-02 | David Robert Vincent | Impurity detection device and method |
| US7201831B2 (en) | 2002-02-22 | 2007-04-10 | Water Security And Technology, Inc. | Impurity detection device |
| US7189314B1 (en) * | 2002-09-06 | 2007-03-13 | Sensicore, Inc. | Method and apparatus for quantitative analysis |
| US8016991B2 (en) * | 2003-04-22 | 2011-09-13 | Robert Bosch Gmbh | Potentiometric sensor device |
| US7875164B2 (en) | 2005-04-22 | 2011-01-25 | Adamant Technologies Sa | Method for use of an electrochemical sensor and electrodes forming said sensor |
| EP1715334A1 (en) * | 2005-04-22 | 2006-10-25 | Adamant Technologies SA | Procedure utilising an electrochemical sensor and electrodes forming the sensor |
| EP1977226A1 (en) * | 2006-01-27 | 2008-10-08 | Intellitect Water Limited | An interdigitated microelectrode and a process for producing the interdigitated microelectrode |
| US20160319522A1 (en) * | 2013-12-20 | 2016-11-03 | Orbital Systems Ab | A water hybrid device |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2290617B (en) | 1998-12-23 |
| GB9415711D0 (en) | 1994-09-21 |
| GB9412820D0 (en) | 1994-08-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20080803 |