Sensor system

Claim 1

A sensor system for determining the pH of a liquid medium characterized in that it comprises, in combination, a first fluorescent indicator whose fluorescence emission is insensitive to pH and a second fluorescent indicator whose fluorescence emission is highly sensitive to solution pH, which indicator combination is adapted to respond when a source of excitation radiation of wavelength λ o is applied to the system such that said first fluorescent indicator is selectively excited by said excitation radiation to emit pH-insensitive fluorescence emission at wavelength λ ₁, emission overlaps the excitation radiation spectrum of said second fluorescent indicator, and said second indicator being excited by said emission radiation of wavelength λ ₁ and in turn emitting a pH-dependent fluorescence emission of wavelength λ ₂, the ratio of intensities of the radiation of wavelengths λ ₁/ λ ₂ providing a highly accurate, stable determination of the pH of said liquid medium.

Claim 5

A method for determining the pH of a liquid medium, characterized in that it comprises contacting said medium with a sensor system comprising, in combination, a first fluorescent indicator whose fluorescence emission is insensitive to pH and a second fluorescent indicator whose fluorescence emission is highly sensitive to solution pH, subjecting said sensor system to excitation radiation of a predetermined wavelength λ o, thereby selectively exciting said first fluorescent indicator to emit a pH-insensitive fluorescence emission at a wavelength of λ ₁, which emission overlaps the excitation radiation spectrum of said second fluorescent indicator and thus excites said second indicator to emit a pH-dependent fluorescence emission of wavelength λ ₂, and measuring either (i) the ratio of intensities of the emitted radiation of wavelengths λ ₁/λ ₂, or (ii) the ratio derived from the intensity of the emitted radiation of wavelength       ₁ and the intensity at the isobestic point between the emission curves of said first and second indications, thereby obtaining a highly accurate, stable determination of the pH of said liquid medium.

Claim 6

A method for determining the pH of a liquid medium, characterized in that it comprises contacting said medium with a sensor system comprising, in combination, a first fluorescent indicator whose fluorescence emission is insensitive to pH and a second fluorescent indicator whose fluorescence emission is highly sensitive to solution pH, subjecting said sensor system to excitation radiation of a predetermined wavelength λ o, thereby selectively exciting said first fluorescent indicator to emit a pH-insensitive fluorescence emission at a wavelength of λ ₁, which emission overlaps the excitation radiation spectrum of said second fluorescent indicator and thus excites said second indicator to emit a pH-dependent fluorescence emission of wavelength λ ₂, and measuring either (i) the ratio of intensities of the emitted radiation of wavelengths λ ₁/λ ₂, or (ii) the ratio derived from the intensity of the emitted radiation of wavelength       ₁ and the intensity at the isobestic point between the emission curves of said first and second indications, thereby obtaining a highly accurate, stable determination of the pH of said liquid medium.

Claim 11

A method for determining the concentration of carbon dioxide in a liquid medium, characterized in that it comprises contacting said medium with a sensor system comprising, in combination, a first fluorescent indicator whose fluorescence emission is insensitive to pH and a second fluorescent indicator whose fluorescence emission is highly sensitive to solution pH, which indicators are associated with a bicarbonate solution bounded by a carbon dioxide-permeable membrane, subjecting said sensor system to excitation radiation of a predetermined wavelength λ o, thereby selectively exciting said first fluorescent indicator to emit a pH-insensitive fluorescence emission at a wavelength of λ ₁, which emission overlaps the excitation radiation spectrum of said second fluorescent indicator and thus excites said second indicator to emit a pH-dependent fluorescent emission of wavelength λ ₂, and measuring either (i) the ratio of intensities of the emitted radiation of wavelengths λ ₁/λ ₂, or (ii) the ratio derived from the intensity of the emitted radiation of wavelength       ₁ and the intensity at the isobestic point between the emission curves of said first and second indications, thereby obtaining an indication of the solution pH within the membrane and thus a highly accurate, stable determination of the concentration of carbon dioxide in the liquid medium.

Claim 12

A method for determining the concentration of carbon dioxide in a liquid medium, characterized in that it comprises contacting said medium with a sensor system comprising, in combination, a first fluorescent indicator whose fluorescence emission is insensitive to pH and a second fluorescent indicator whose fluorescence emission is highly sensitive to solution pH, which indicators are associated with a bicarbonate solution bounded by a carbon dioxide-permeable membrane, subjecting said sensor system to excitation radiation of a predetermined wavelength λ o, thereby selectively exciting said first fluorescent indicator to emit a pH-insensitive fluorescence emission at a wavelength of λ ₁, which emission overlaps the excitation radiation spectrum of said second fluorescent indicator and thus excites said second indicator to emit a pH-dependent fluorescent emission of wavelength λ ₂, and measuring either (i) the ratio of intensities of the emitted radiation of wavelengths λ ₁/λ ₂, or (ii) the ratio derived from the intensity of the emitted radiation of wavelength       ₁ and the intensity at the isobestic point between the emission curves of said first and second indications, thereby obtaining an indication of the solution pH within the membrane and thus a highly accurate, stable determination of the concentration of carbon dioxide in the liquid medium.

Claim 13

A method of measuring the concentration of carbon dioxide in a medium by determining the water content in a pH-independent sensor system comprising an optical fiber having a proximal end and a distal end, said distal end having attached thereto a fluorescence indicator embedded in a carrier matrix with a controlled water content, said carrier matrix containing a miscible mixture of water and non-aqueous solvent in controlled proportions and being separated from said medium by a gas-permeable, water-impermeable diffusion membrane, said indicator, when excited by excitation radiation of a predetermined wavelength λ o, emitting fluorescent emission at a wavelength λ ₂ in the presence of water and at a wavelength λ s in the presence of said non-aqueous solvent, the intensity of each emission being dependent upon the ratio of water to non-aqueous solvent present in the system such that the ratio of the intensities of emitted radiation of wavelengths λ w and λ s is therefore proportional to the amount of water present and diffusion of carbon dioxide through said gas-permeable membrane and subsequent reaction with water to deplete the water content of the system induces a change in the intensities of said emissions, characterized in that it comprises transmitting through said optical fiber, from a source adjacent to its proximal end, excitation radiation of said predetermined wavelength λ o , and measuring the ratio of the intensities of the emitted radiation of wavelengths λ w and λ s , thereby obtaining a determination of the water content and thus a measurement of the carbon dioxide concentration in the surrounding medium.

Claim 14

A method of measuring the concentration of carbon dioxide in a medium by determining the water content in a pH-independent sensor system comprising an optical fiber having a proximal end and a distal end, said distal end having attached thereto a fluorescence indicator embedded in a carrier matrix with a controlled water content, said carrier matrix containing a miscible mixture of water and non-aqueous solvent in controlled proportions and being separated from said medium by a gas-permeable, water-impermeable diffusion membrane, said indicator, when excited by excitation radiation of a predetermined wavelength λ o, emitting fluorescent emission at a wavelength λ ₂ in the presence of water and at a wavelength λ s in the presence of said non-aqueous solvent, the intensity of each emission being dependent upon the ratio of water to non-aqueous solvent present in the system such that the ratio of the intensities of emitted radiation of wavelengths λ w and λ s is therefore proportional to the amount of water present and diffusion of carbon dioxide through said gas-permeable membrane and subsequent reaction with water to deplete the water content of the system induces a change in the intensities of said emissions, characterized in that it comprises transmitting through said optical fiber, from a source adjacent to its proximal end, excitation radiation of said predetermined wavelength λ o , and measuring the ratio of the intensities of the emitted radiation of wavelengths λ w and λ s , thereby obtaining a determination of the water content and thus a measurement of the carbon dioxide concentration in the surrounding medium.