Sensor with improved drift stability
First Claim
1. A sensing composition for sensing a carbon dioxide analyte, comprising:
- an aqueous first phase comprising a pH sensitive indicator component in a buffer solution, wherein said buffer solution comprises less than 100 mM of a bicarbonate ion, wherein the concentration of said pH sensitive indicator component in said sensing composition is effective to provide a signal in response to the concentration of carbon dioxide in a medium to which said sensing composition is exposed, said carbon dioxide being effective to alter the pH of said aqueous phase; and
a hydrophobic second phase which is permeable to said analyte and impermeable to ionized hydrogen, wherein said aqueous phase is dispersed within said hydrophobic phase, and wherein said sensing composition is substantially free of partitioning species, other than the analyte of interest, which migrate between said phases in response to a change in pH in said aqueous phase or between the sensing composition and the medium and which migration substantially affects said concentration dependent signal.
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Abstract
The present invention provides an optical fluorescence based sensor for measuring the concentration of a gas (e.g., CO2 or ammonia) in a medium such as blood which has improved drift stability. In a preferred embodiment, the sensors of the present invention comprise microcompartments of an aqueous phase having a pH sensitive sensing component within a hydrophobic barrier phase. The sensors of the present invention are substantially free of partitioning species other than the analyte of interest which can migrate from one phase to the other in response to a change in pH in the aqueous phase and which substantially affect the concentration dependent signal. In an alternative embodiment, the sensors of the present invention are constructed so as to retard the migration of partitioning species, thus reducing the initial rate of drift.
50 Citations
48 Claims
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1. A sensing composition for sensing a carbon dioxide analyte, comprising:
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an aqueous first phase comprising a pH sensitive indicator component in a buffer solution, wherein said buffer solution comprises less than 100 mM of a bicarbonate ion, wherein the concentration of said pH sensitive indicator component in said sensing composition is effective to provide a signal in response to the concentration of carbon dioxide in a medium to which said sensing composition is exposed, said carbon dioxide being effective to alter the pH of said aqueous phase; and a hydrophobic second phase which is permeable to said analyte and impermeable to ionized hydrogen, wherein said aqueous phase is dispersed within said hydrophobic phase, and wherein said sensing composition is substantially free of partitioning species, other than the analyte of interest, which migrate between said phases in response to a change in pH in said aqueous phase or between the sensing composition and the medium and which migration substantially affects said concentration dependent signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A sensing composition for sensing carbon dioxide, comprising:
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an aqueous first phase comprising a pH sensitive indicator component, wherein the concentration of said pH sensitive indicator component in said sensing composition is effective to provide a signal in response to the concentration of carbon dioxide in a medium to which said sensing composition is exposed, said carbon dioxide being effective to alter the pH of said aqueous phase; and a hydrophobic second phase which is permeable to said analyte and impermeable to ionized hydrogen, wherein said aqueous phase is dispersed within said hydrophobic phase, and wherein said sensing composition comprises less than 1 mM of acidic or basic partitioning species, other than the analyte of interest, which migrate between said phases in response to a change in pH in said aqueous phase or between the sensing composition and the medium and which migration substantially affects said concentration dependent signal. - View Dependent Claims (20)
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21. A sensing composition for sensing carbon dioxide, comprising:
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an aqueous first phase comprising an effective amount of a pH sensitive indicator component in a buffer solution, wherein said buffer solution has a buffering capacity equivalent to a solution prepared with up to 20 mM of said pH sensitive indicator component, between 20 and 100 mM of a bicarbonate salt, and up to 50 mM of a 50;
50 mix of a monobasic and dibasic phosphates salt, wherein said pH sensitive indicator component is effective to provide a signal in response to the concentration of carbon dioxide in a medium to which said sensing composition is exposed, said carbon dioxide being effective to alter the pH of said aqueous phase; anda hydrophobic second phase which is permeable to said analyte and impermeable to ionized hydrogen, wherein said aqueous phase is dispersed within said hydrophobic phase, wherein said sensing composition is substantially free of acidic partitioning species, other than the analyte of interest, which migrate between said phases in response to a change in pH in said aqueous phase or between the sensing composition and the medium and which migration substantially affects said concentration dependent signal, wherein said sensing composition, immediately after being equilibrated in a first medium having a pCO2 of 0.25 mmHg, provides a measurement of CO2 partial pressure which drifts less than 12% over a three hour period when moved from said first medium to a second medium having a pCO2 of 45.6 mmHg, and wherein said sensing composition has a specific sensitivity between 0.2 and 0.5. - View Dependent Claims (22, 23, 24, 25)
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26. A sensing composition for sensing carbon dioxide, comprising:
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an aqueous first phase comprising an effective amount of a pH sensitive indicator component in a buffer solution, wherein said buffer solution has a buffering capacity equivalent to a solution prepared with up to 20 mM of said pH sensitive indicator component, at least 20 mM of a bicarbonate salt, and up to 50 mM of a 50;
50 mix of a monobasic and dibasic phosphates salt, wherein said pH sensitive indicator component is effective to provide a signal in response to the concentration of carbon dioxide in a medium to which said sensing composition is exposed, said carbon dioxide being effective to alter the pH of said aqueous phase; anda hydrophobic second phase which is permeable to said analyte and impermeable to ionized hydrogen, wherein said aqueous phase is dispersed within said hydrophobic phase, wherein said sensing composition is substantially free of acidic partitioning species, other than the analyte of interest, which migrate between said phases in response to a change in pH in said aqueous phase or between the sensing composition and the medium and which migration substantially affects said concentration dependent signal, wherein said sensing composition, immediately after being equilibrated in a first medium having a pCO2 of 0.25 mmHg, provides a measurement of CO2 partial pressure which drifts less than 12% over a three hour period when moved from said first medium to a second medium having a pCO2 of 45.6 mmHg, wherein said sensing composition has a specific sensitivity between 0.2 and 0.5, and wherein said aqueous phase does not include the combination of HPTS and polyvinylpyrolidone. - View Dependent Claims (27, 28, 29, 30)
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31. A sensing composition for sensing carbon dioxide, comprising:
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an aqueous first phase comprising a pH sensitive indicator component in a buffer solution, wherein said buffer solution has a buffering capacity equivalent to a solution prepared with said pH sensitive indicator component and at least one of a bicarbonate salt and a 50;
50 mixture of a monobasic phosphate salt and a dibasic phosphate salt, wherein the sum of the molar concentration of the indicator component and one-half of the molar concentration of the mixture of phosphate salts divided by the molar concentration of the bicarbonate salt is at least 0.66, wherein said pH sensitive indicator component is effective to provide a signal in response to the concentration of carbon dioxide in a medium to which said sensing composition is exposed, said carbon dioxide being effective to alter the pH of said aqueous phase; anda hydrophobic second phase which is permeable to said analyte and impermeable to ionized hydrogen, wherein said aqueous phase is dispersed within said hydrophobic phase, wherein said sensing composition is substantially free of basic partitioning species, other than the analyte of interest, which migrate between said phases in response to a change in pH in said aqueous phase or between the sensing composition and the medium and which migration substantially affects said concentration dependent signal, wherein said sensing composition, immediately after being equilibrated in a first medium having a pCO2 of 0.25 mmHg, provides a measurement of CO2 partial pressure which drifts less than 12% over a three hour period when moved from said first medium to a second medium having a pCO2 of 45.6 mmHg, and wherein said sensing composition has a specific sensitivity between 0.2 and 0.5. - View Dependent Claims (32, 33, 34, 35)
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36. A sensing composition for sensing carbon dioxide, comprising:
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an aqueous first phase comprising a pH sensitive indicator component in a buffer solution, wherein said buffer solution has a buffering capacity equivalent to a solution prepared with said pH sensitive indicator component, at least 15 mM of a bicarbonate salt, and up to 50 mM of a 50;
50 mixture of a monobasic and dibasic phosphate salt, wherein the ratio of the sum of the molar concentration of the indicator component and one-half of the molar concentration of the mixture of phosphate salts divided by the molar concentration of the bicarbonate salt is at least 0.66, wherein said pH sensitive indicator component is effective to provide a signal in response to the concentration of carbon dioxide in a medium to which said sensing composition is exposed, said carbon dioxide being effective to alter the pH of said aqueous phase; anda hydrophobic second phase which is permeable to said analyte and impermeable to ionized hydrogen, wherein said aqueous phase is dispersed within said hydrophobic phase, wherein said sensing composition, immediately after being equilibrated in a first medium having a pCO2 of 0.25 mmHg, provides a measurement of CO2 partial pressure which drifts less than 12% over a three hour period when moved from said first medium to a second medium having a pCO2 of 45.6 mmHg, and wherein said sensing composition has a specific sensitivity between 0.2 and 0.5. - View Dependent Claims (37, 38, 39, 40)
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41. A sensing composition, comprising:
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an aqueous first phase comprising an indicator component, wherein said pH sensitive indicator component is effective to provide a signal in response to the concentration of an analyte in a medium to which said sensing composition is exposed, said analyte being effective to alter the pH of said aqueous phase; and a hydrophobic second phase which is permeable to said analyte and impermeable to ionized hydrogen, wherein said aqueous phase is contained within the pores of an asymmetrical membrane, said membrane having a first surface having small pore openings and a second surface having large pore openings, and wherein said hydrophobic phase covers said first surface. - View Dependent Claims (42)
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43. A sensing composition for sensing a carbon dioxide analyte, comprising:
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an aqueous first phase comprising a pH sensitive indicator component, a buffer solution containing less than 100 mM of a bicarbonate ion, and a hydrogel of a hydrophilic polymer, wherein the concentration of said pH sensitive indicator component in said sensing composition is effective to provide a signal in response to the concentration of carbon dioxide in a medium to which said sensing composition is exposed, said carbon dioxide being effective to alter the pH of said aqueous phase; and a hydrophobic second phase which is permeable to said analyte and impermeable to ionized hydrogen, wherein said sensing composition is substantially free of partitioning species, other than the analyte of interest, which migrate between said phases in response to a change in pH in said aqueous phase or between the sensing composition and the medium and which migration substantially affects said concentration dependent signal. - View Dependent Claims (44, 45, 46, 47, 48)
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Specification