US4818361A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Combined pH and dissolved carbon dioxide gas sensor
Assignee: Mallinckrodt Sensor Systems Inc
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Filing: 1987-11-30
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Granted: 1989-04-04
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Expires: 2007-11-30
Abstract
Abstract A combination pH and CO 2 sensor employs separate sensors. Each sensor has a wire with an electrochemically active layer, an electrolyte layer and a membrane between the electrolyte layer and the fluid to be tested. Each electrolyte layer is constructed of a dried residue which can be easily stored and which must be rehydrated prior to the first use. The electrolyte layer in the pH sensor when hydrated forms an aqueous solution buffered against changes in pH due to changes in the dissolved CO 2 concentration and is preferably formed of 2-(n-morpholino) ethanesulfonic acid, 2-(n-morpholino) ethanesulfonic acid - sodium salt and potassium chloride. The electrolyte layer in the CO 2 sensor when hydrated forms an aqueous solution having bicarbonate ions and is preferably formed of polyvinyl alcohol, sodium chloride and sodium bicarbonate. The electrical potential at the pH sensor is proportional to the pH of the fluid. The electrical potential difference between the CO 2 sensor and the pH sensor is proportional to the concentration of dissolved CO 2 in the fluid. In the preferred embodiment the two sensors are formed in a sensor assembly with the fluid pumped through a channel. This invention is readily adaptable to a storage stable disposable assembly.
Inventors
- 👤 Bruce Burgess
- 👤 Glenn Martin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 04:00
CPC Classifications
G; G01; G01N; G01N33/00; G01N33/48; G01N33/483; G01N33/487; G01N33/49; G01N33/492; G01N27/00; G01N27/26; G01N27/416; G01N27/4166; G01N27/4167; G01N33/4915; G01N27/28; G01N27/30; G01N27/333; G01N27/3335; G01N33/4925
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
583 words
An apparatus for measuring pH and the concentration of dissolved CO 2 in a fluid comprising: a measurement chamber for containing a sample of fluid to be measured; a pH sensor including a first wire having first and second ends, said first end exposed for electrical contact thereto, a first electrochemically active layer disposed covering said second end of said first wire for forming an electrochemical coupling to said first wire, a first dried electrolyte layer disposed covering said first electrochemically active layer, said first dried electrolyte layer when hydrated forming an aqueous solution buffered against changes in pH due to changes in dissolved CO 2 concentration, and a first membrane having an outer surface exposed to the fluid in the said measurement chamber and an inner surface covering said first electrolyte layer, said first membrane being sensitive to the difference in pH between the inner and outer surfaces thereof to form an electrical potential thereacross and being water permeable; a CO 2 sensor including a second wire having first and second ends, said first end exposed for electrical contact thereto, a second electrochemically active layer disposed covering said second end of said second wire for forming an electrochemical coupling to said second wire, a second dried electrolyte layer disposed covering said second electrochemically active layer, said second dried electrolyte layer when hydrated forming an aqueous solution including bicarbonate ions, and a second membrane having an outer surface exposed to the fluid in said measurement chamber and an inner surface covering said second electrolyte layer, said second membrane being sensitive to the difference in pH between the inner and outer surfaces thereof to form an electrical potential thereacross and being water and dissolved CO 2 permeable; a ground electrode disposed in electrical contact with the fluid in said measurement chamber; a reference electrode disposed in electrical contact with the fluid in said measurement chamber for providing a stable reference potential independent of ionic activity of the fluid in said reference chamber; and an electrical circuit connected to said first ends of said first and second wires including a first differential signal means connected to said first wire and said ground electrode for generating a first difference signal proportional to the electrical potential difference between said first wire and said ground electrode, a second differential signal means connected to said second wire and said ground electrode for generating a second difference signal proportional to the electrical potential difference between said second wire and said ground electrode, a third differential signal means connected to said reference electrode and said ground electrode for generating a third difference signal proportional to the electrical potential difference between said reference electrode and said ground electrode, a fourth differential signal means connected to said first differential signal means and said third differential signal means for generating a fourth difference signal proportional to the electrical potential difference between said first difference signal and said third difference signal, said fourth difference signal being said pH signal, a fifth differential signal means connected to said second and third differential signal means for generating a fifth difference signal proportional to the electrical potential difference between said second difference signal and said third difference signal, and a sixth differential signal means connected to said fourth differential signal means and said fifth differential signal means for generating a sixth difference signal proportional to the electrical potential difference between said fourth difference signal and said fifth difference signal, said sixth difference signal being said CO 2 signal.
Claim 2
Independent Claim
583 words
An apparatus for measuring pH and the concentration of dissolved CO 2 in a fluid comprising: a measurement chamber for containing a sample of fluid to be measured; a pH sensor including a first wire having first and second ends, said first end exposed for electrical contact thereto, a first electrochemically active layer disposed covering said second end of said first wire for forming an electrochemical coupling to said first wire, a first dried electrolyte layer disposed covering said first electrochemically active layer, said first dried electrolyte layer when hydrated forming an aqueous solution buffered against changes in pH due to changes in dissolved CO 2 concentration, and a first membrane having an outer surface exposed to the fluid in the said measurement chamber and an inner surface covering said first electrolyte layer, said first membrane being sensitive to the difference in pH between the inner and outer surfaces thereof to form an electrical potential thereacross and being water permeable; a CO 2 sensor including a second wire having first and second ends, said first end exposed for electrical contact thereto, a second electrochemically active layer disposed covering said second end of said second wire for forming an electrochemical coupling to said second wire, a second dried electrolyte layer disposed covering said second electrochemically active layer, said second dried electrolyte layer when hydrated forming an aqueous solution including bicarbonate ions, and a second membrane having an outer surface exposed to the fluid in said measurement chamber and an inner surface covering said second electrolyte layer, said second membrane being sensitive to the difference in pH between the inner and outer surfaces thereof to form an electrical potential thereacross and being water and dissolved CO 2 permeable; a ground electrode disposed in electrical contact with the fluid in said measurement chamber; a reference electrode disposed in electrical contact with the fluid in said measurement chamber for providing a stable reference potential independent of ionic activity of the fluid in said reference chamber; and an electrical circuit connected to said first ends of said first and second wires including a first differential signal means connected to said first wire and said ground electrode for generating a first difference signal proportional to the electrical potential difference between said first wire and said ground electrode, a second differential signal means connected to said second wire and said ground electrode for generating a second difference signal proportional to the electrical potential difference between said second wire and said ground electrode, a third differential signal means connected to said reference electrode and said ground electrode for generating a third difference signal proportional to the electrical potential difference between said reference electrode and said ground electrode, a fourth differential signal means connected to said first differential signal means and said third differential signal means for generating a fourth difference signal proportional to the electrical potential difference between said first difference signal and said third difference signal, said fourth difference signal being said pH signal, a fifth differential signal means connected to said second and third differential signal means for generating a fifth difference signal proportional to the electrical potential difference between said second difference signal and said third difference signal, and a sixth differential signal means connected to said fourth differential signal means and said fifth differential signal means for generating a sixth difference signal proportional to the electrical potential difference between said fourth difference signal and said fifth difference signal, said sixth difference signal being said CO 2 signal.
Claim 3
Dependent Claim
19 words
The apparatus claimed in claim 1, wherein: said first wire and said second wires are each composed of silver.
Claim 4
Dependent Claim
20 words
The apparatus claimed in claim 2, wherein: said first and second electrochemically active layers are each composed of silver chloride.
Claim 5
Dependent Claim
43 words
The apparatus as claimed in claim 1, wherein: said first dried electrolyte layer is composed of the dried residue of an aqueous solution of 0.024 molar 2-(n-morpholino) ethanesulfonic acid, 0.024 molar 2-(n-morpholino) ethanesulfonic acid - sodium salt and 5.0×10 -6 molar potassium chloride.
Claim 6
Dependent Claim
22 words
The apparatus claimed in claim 1, wherein: said second dried electrolyte layer is composed of at least one salt which includes bicarbonate.
Claim 7
Dependent Claim
38 words
The apparatus claimed in claim 1, wherein: said second dried electrolyte layer is composed of at least one salt which includes bicarbonate and a hydrophilic material in an amount for providing the degree of hydration desired upon rehydration.
Claim 8
Dependent Claim
45 words
The apparatus claimed in claim 1, wherein: said second dried electrolyte layer is composed of the dried residue of an aqueous solution of 4% weight/volume polyvinyl alcohol having a molecular weight of 115,000 and 10% hydrolyzed, 0.0005 molar sodium chloride and 0.005 molar sodium bicarbonate.
Claim 9
Dependent Claim
45 words
The apparatus claimed in claim 1, wherein: said first and second membranes are each composed of the dried residue of a solution of 32.8% polyvinyl chloride, 0.6% potassium tetrakis (4-chlorophenyl) borate, 65.6% bis (2-ethyl hexyl) sebacate, and 1.0% tridodecylamine by weight in an organic solvent.
Claim 10
Dependent Claim
47 words
The apparatus as claimed in claim 1, further comprising: a reference solution chamber for containing a reference solution of known ion concentration in fluid communication with said measurement chamber; and wherein said reference electrode is disposed in electrical contact with the fluid in said reference solution chamber.
Claim 11
Dependent Claim
23 words
The apparatus as claimed in claim 9, wherein: said reference solution chamber includes a capillary section for fluid communication with said measurement chamber.
Claim 12
Dependent Claim
24 words
The apparatus as claimed in claim 1, wherein: said first, second, third, fourth, fifth and sixth differential signal means consist of respective differential amplifiers.
Claim 13
Dependent Claim
151 words
The apparatus as claimed in claim 1, wherein: said first, second and third differential signal means consist of respective differential amplifiers; and said fourth, fifth and sixth differential signal means includes a conversion means connected to said said first, second and third differential signal means for generating respective first, second and third digital difference signals corresponding to said first, second and third difference signals, and a digital processing system connected to said conversion means for forming said fourth difference signal by digital subtraction of said first digital difference signal and said third digital difference signal, said fourth difference signal being said pH signal, forming said fifth difference signal by digital subtraction of said second digital difference signal and said third digital difference signal, and forming said sixth difference signal by digital subtraction of said fifth difference signal and said fourth difference signal, said sixth difference signal being said CO 2 signal.
Claim 14
Dependent Claim
192 words
The apparatus as claimed in claim 12, wherein: said conversion means includes a first sample and hold circuit connected to said first differential signal means for sampling and holding said first difference signal, a second sample and hold circuit connected to said second differential signal means for sampling and holding said second difference signal, a third sample and hold circuit connected to said third differential signal means for sampling and holding said third difference signal, a multiplexer having first, second and third inputs connected respectively to said first, second and third sample and hold circuits and having an output, for coupling a selected one of said first, second and third inputs to said output, and an analog to digital converter connected to said output of said multiplexer for generating a first digital difference signal when said multiplexer couples said first input to said output, a second digital difference signal when said multiplexer couples said second input to said output, and a third digital difference signal when said multiplexer couples said third input to said output; and said digital processing system includes a microprocessor control means connected to said analog to digital converter.
Claim 15
Dependent Claim
33 words
The apparatus as claimed in claim 13, further comprising: an output means connected to said microprocessor control means for generating an operator perceivable indication of said pH signal and said CO 2 signal.
Claim 16
Dependent Claim
15 words
The apparatus claimed in claim 14, wherein: said output means comprises a visual display means.
Claim 17
Dependent Claim
13 words
The apparatus claimed in claim 14, wherein: said output means comprises a printer.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-04-03 | 1992-10-03 | 1993-04-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-04-03 | 1996-10-03 | 1997-04-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-04-03 | 2000-10-03 | 2001-04-04 | $7700.00 | Window Closed / Lapsed |