WO1996025662A1 - Analyse d'un liquide aqueux - Google Patents

Analyse d'un liquide aqueux Download PDF

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Publication number
WO1996025662A1
WO1996025662A1 PCT/GB1996/000338 GB9600338W WO9625662A1 WO 1996025662 A1 WO1996025662 A1 WO 1996025662A1 GB 9600338 W GB9600338 W GB 9600338W WO 9625662 A1 WO9625662 A1 WO 9625662A1
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WO
WIPO (PCT)
Prior art keywords
liquid
sensor
region
condition
electrode
Prior art date
Application number
PCT/GB1996/000338
Other languages
English (en)
Inventor
Andrew Nigel Sloper
Ronald Briggs
William Douglas Meredith
Alan Dodgson
Original Assignee
M Squared Technology Limited
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by M Squared Technology Limited filed Critical M Squared Technology Limited
Priority to AU46716/96A priority Critical patent/AU4671696A/en
Publication of WO1996025662A1 publication Critical patent/WO1996025662A1/fr

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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
    • G01N27/416—Systems
    • G01N27/42—Measuring deposition or liberation of materials from an electrolyte; Coulometry, i.e. measuring coulomb-equivalent of material in an electrolyte
    • G01N27/44—Measuring deposition or liberation of materials from an electrolyte; Coulometry, i.e. measuring coulomb-equivalent of material in an electrolyte using electrolysis to generate a reagent, e.g. for titration

Definitions

  • This invention relates to a method and apparatus for detecting a condition in an aqueous liquid using a sensor .
  • a method of detecting a condition in an aqueous liquid which comprises using a sensor to detect said condition in a detection region of said liquid the liquid in said region being electrocnemicallv modified for said detection.
  • apparatus for detecting a condition in an aqueous liquid which apparatus comprises a sensor for detecting said condition, in a detection region of the liquid, and means for electrochemically modifying the liquid in said region for said detection.
  • the electrochemical modification of the liquid under test need not cause any permanent change in the liquid
  • the electrochemical modification of the liquid under test need not cause any permanent change in the liquid
  • the nature and arrangement of the electrodes will be chosen in dependence on the effects required and the nature of the test
  • platinum electrodes such as pieces of platinum gauze
  • solid, woven, porous or film electrodes of materials such as gold, silver, platinum, stainless steel or vitreous carbon, conducting polymers etc can also be used to achieve pH or other variations in the sample solution.
  • the spacing of the electrodes (one being positioned to affect the pH in the measurement region, and the other not) should be sufficient to avoid interference between the two. In static liquids, a separation of a few mm for example can be used.
  • Electrodes may be driven by a constant voltage or constant current source, that this source may be pulsed or modulated if required, and that the polarity on the electrodes may be reversed periodically as part of an electrochemical cleaning procedure
  • one electrode In the case of detecting the condition of an essentially static liquid using a sensor having a surface which contacts the liquid, one electrode is located close to the sensor surface. The modified pH is then generated near the sensor surface. When, however, the liquid under test is flowing, the pH-modifying electrode can be upstream of the sensor detection region if desired. The modified pH liquid then flows downstream from the electrode to the region where the sensor is operating.
  • a liquid flow channel is provided adjacent the sensor surface with an electrode therein upstream of the sensor surface.
  • the electrode can be within the sensor surface if desired, or it may be adjacent the surface or spaced therefrom.
  • the electrodes are arranged in any manner suited to providing the desired pH in the detection region.
  • the arrangement can be generally as
  • the senor can be located just above the liquid surface to sense gas accumulating there.
  • the anode and/or the cathode can be formed in two or more parts, located spaced apart, in the liquid under test if desired.
  • sensors used in the present invention is not critical. They can be electrical, optical or any other type of sensor and, as described, they may be invasive or non-invasive.
  • Fig. 1 is a schematic vertical sectional view of an invasive sensor measurement arrangement of static fluid
  • Fig. 2 is a schematic part-sectional view of an invasive sensor measurement arrangement of flowing fluid.
  • Fig. 3 is a plot of ammonia concentration against sensor potential, as described hereafter in the Example
  • a sensor 1 dipping into a liquid 2 which is to be tested for a
  • the sensor has an end surface 3 which is the sensitive region of the sensor.
  • an electrode 4 which in this case is a cathode arranged to generate hydroxyl ions on its surface and in the immediately surrounding area (shaded 5).
  • area 5 includes the space 6 6etween the sensor surface 3 and the electrode 4.
  • the counter electrode 7 (in this case the anode) is located elsewhere in the liquid, and both electrodes are connected (not shown) to an
  • Fig. 1 shows one possible arrangement, and that the electrode can be closer to the sensor surface or can form a part of it, in other embodiments.
  • the electrochemical electrodes 4 and 7 are identical to The electrochemical electrodes 4 and 7 are identical to The electrochemical electrodes 4 and 7 are identical to The electrochemical electrodes 4 and 7 are identical to The electrochemical electrodes 4 and 7 are identical to The electrochemical electrodes 4 and 7 are identical to The electrochemical electrodes 4 and 7 are identical to The electrochemical electrodes 4 and 7 are identical to The electrochemical electrodes 4 and 7 are identical to The electrochemical electrodes 4 and 7 are identical to The electrochemical electrodes 4 and 7 are the electrochemical electrodes 4
  • a pH sensor eg. a micro pH electrode with a feedback control loop
  • the electrode current can then be controlled as necessary to generate and maintain the desired pH.
  • a flow partitioner 14 extending parallel to the electrode surface 13 and beyond it at both ends.
  • Partitioner 14 forms together with the wall of conduit 10 and the surface 13 of sensor 12, a flow channel 15. At the upstream end of flow channel 15 is the first electrode 16 of the electrochemical means. The second electrode 17 is in the main flow part of the conduit. Both electrodes 16, 17 are connected to an electrical source (not shown)
  • electrode 16 In operation, electrode 16 generates hydrogen ions or hydroxyl ions (depending on its polarity), and these ions are swept through flow channel 15 by the flowing liquid.
  • This region includes the area immediately adjacent the sensor surface 13 which is the measurement region.
  • a localised modified pH is provided at the sensor for the condition detector.
  • sensor surface 13 can be spaced above the liquid and gases to be measured, eg. ammonia, can then accumulate at the sensor surface.
  • means may be provided to monitor the pH in flow channel 15 and to control the electrode current to provide and maintain the desired pH. Also, the net effect upon the liquid 10 is nil: shortly downstream of the partitioner 14, the pH is uniform and the same as that of the liquid upstream of the
  • the method and apparatus of the invention can be used for the detection of ammonia and of chlorine in aqueous liquids Ammonia dissolves and
  • the concentration of the unionised (gaseous) and ionised forms of ammonia are dependent on the pH of the sample.
  • the concentration of the ionised form at neutral pH is minute (approximately 0.2%) so, since the only satisfactory methods of monitoring total ammonia are based on the determination of unionised (gaseous) ammonia, it is standard practice to add sodium hydroxide to raise the pH to greater than 11 to convert all the ammonia to the unionised (gaseous) form.
  • the addition of sodium hydroxide can be avoided by raising the pH in the region of the sensor, by electrochemical means.
  • Chlorine dissolves in water and generally dissociates according to the following formulae:
  • the pH is lowered electrochemically to below 5 to convert all the chlorine to the unionised form so that total chlorine can be measured independent of the pH of the sample. Measurements at normal sample pH and at low pH, together with sample pH measurement, can give total free chlorine and ionised OCl- determinations.
  • the method and apparatus of the invention can be used on the opposite side of a sensor membrane to the sample.
  • the sensor membrane will be
  • the means for electrochemically modifying the liquid is disposed in the reservoir, ie. on the opposite side of the sensor membrane to the sample.
  • the liquid in the reservoir can be electrochemically modified for detection of a
  • the sensor membrane can allow Cl 2 and the unionised HOCl to diffuse therethrough into the sensor reservoir.
  • the pH of these species can then be raised by means of
  • the concentration of the OCl- can be determined by measuring its light absorption
  • An ammonia gas permeable membrane sensor is provided with an end cap containing two platinum gauze electrodes.
  • the planar surfaces of the two platinum gauze electrodes are positoned parallel and adjacent to each other with a spacing of approximately 6mm.
  • the end cap is attached to the ammonia gas permeable membrane sensor with one of the electrodes, the cathode, close to the sensor surface.
  • a voltage of approximately 2.3 volts is applied to the electrodes to generate hydroxyl ions at the cathode surface to cause a localised increase in the pH.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Molecular Biology (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

Lorsque l'on utilise un capteur (1) pour détecter une condition dans un liquide (2), on évite d'avoir à ajouter des réactifs (par exemple des acides, des bases, des tampons) en utilisant des moyens électrochimiques (4, 7) pour produire l'environnement approprié dans la zone de détection du capteur (1). On peut utiliser l'électrode (4) pour augmenter ou abaisser un pH, en tant que de besoin pour permettre la mesure par le capteur. Celui-ci peut être ou ne pas être en contact avec le liquide (2).
PCT/GB1996/000338 1995-02-13 1996-02-13 Analyse d'un liquide aqueux WO1996025662A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU46716/96A AU4671696A (en) 1995-02-13 1996-02-13 Aqueous liquid analysis

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9502740.5 1995-02-13
GBGB9502740.5A GB9502740D0 (en) 1995-02-13 1995-02-13 Aqueous liquid analysis

Publications (1)

Publication Number Publication Date
WO1996025662A1 true WO1996025662A1 (fr) 1996-08-22

Family

ID=10769489

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1996/000338 WO1996025662A1 (fr) 1995-02-13 1996-02-13 Analyse d'un liquide aqueux

Country Status (3)

Country Link
AU (1) AU4671696A (fr)
GB (1) GB9502740D0 (fr)
WO (1) WO1996025662A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998022813A1 (fr) * 1996-11-21 1998-05-28 Enviros Monitors Limited Dispositif et procede d'alteration du ph
GB2337056A (en) * 1996-11-21 1999-11-10 Enviros Monitors Limited PH altering device and method
EP1260813A1 (fr) * 2001-05-22 2002-11-27 CSEM Centre Suisse d'Electronique et de Microtechnique SA Système d'électrodes pour capteur électrochimique
US7201831B2 (en) 2002-02-22 2007-04-10 Water Security And Technology, Inc. Impurity detection device
US8221597B2 (en) * 2006-01-05 2012-07-17 Samsung Electronics Co., Ltd. Apparatus and method for adjusting pH of solution

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3897315A (en) * 1973-04-09 1975-07-29 Orion Research Method of determining hydrogen sulfide
US3959087A (en) * 1969-09-05 1976-05-25 Fischer & Porter Co. In-line residual chlorine analyzer
US4666565A (en) * 1983-04-28 1987-05-19 British Gas Corporation Gas sensor and method
EP0543770A2 (fr) * 1988-03-31 1993-05-26 ORBISPHERE LABORATORIES (INC.), Wilmington, Succursale de Collonge-Bellerive Détection d'ozone
WO1993022668A1 (fr) * 1992-04-23 1993-11-11 Central Research Laboratories Limited Procede et appareil pour determiner la concentration d'ions ammonium en solution

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3959087A (en) * 1969-09-05 1976-05-25 Fischer & Porter Co. In-line residual chlorine analyzer
US3897315A (en) * 1973-04-09 1975-07-29 Orion Research Method of determining hydrogen sulfide
US4666565A (en) * 1983-04-28 1987-05-19 British Gas Corporation Gas sensor and method
EP0543770A2 (fr) * 1988-03-31 1993-05-26 ORBISPHERE LABORATORIES (INC.), Wilmington, Succursale de Collonge-Bellerive Détection d'ozone
WO1993022668A1 (fr) * 1992-04-23 1993-11-11 Central Research Laboratories Limited Procede et appareil pour determiner la concentration d'ions ammonium en solution

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
VAN DEN BERG A ET AL: "On-wafer fabricated free-chlorine sensor with ppb detection limit for drinking-water monitoring", FOURTH INTERNATIONAL MEETING ON CHEMICAL SENSORS, TOKYO, JAPAN, 13-17 SEPT. 1992, SENSORS AND ACTUATORS B (CHEMICAL), MAY 1993, SWITZERLAND, pages 396 - 399, XP002002708 *

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998022813A1 (fr) * 1996-11-21 1998-05-28 Enviros Monitors Limited Dispositif et procede d'alteration du ph
GB2337056A (en) * 1996-11-21 1999-11-10 Enviros Monitors Limited PH altering device and method
EP1260813A1 (fr) * 2001-05-22 2002-11-27 CSEM Centre Suisse d'Electronique et de Microtechnique SA Système d'électrodes pour capteur électrochimique
US7201831B2 (en) 2002-02-22 2007-04-10 Water Security And Technology, Inc. Impurity detection device
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
US8221597B2 (en) * 2006-01-05 2012-07-17 Samsung Electronics Co., Ltd. Apparatus and method for adjusting pH of solution
US8524059B2 (en) 2006-01-05 2013-09-03 Samsung Electronics Co., Ltd. Apparatus and method for adjusting pH of solution

Also Published As

Publication number Publication date
GB9502740D0 (en) 1995-03-29
AU4671696A (en) 1996-09-04

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