Osmolarity sensor
First Claim
1. An osmolarity sensor for measuring an osmolarity of a specimen solution, comprising:
- means for containing a standard solution including an aqueous solution of electrolytes;
said means for containing defining a cavity, which is variable in volume, wherein the standard solution is held;
said means for containing including a vapor-permeable membrane separating the standard solution from the specimen solution;
said vapor-permeable membrane permitting passage of water vapor of the specimen solution and the standard solution, and blocking passage of solutes of said specimen solution; and
means for sensing one of a conductivity and an absorbance of the standard solution, independent of positioning of said means for containing, and means, responsive to said means for sensing, for determining the osmolarity of the specimen solution when the standard solution has achieved substantial osmotic equilibrium with the specimen solution.
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Abstract
An osmolarity sensor continuously senses an osmolarity of a fluid. A principle of operation is based on achieving an equilibrium of a vapor pressure of a specimen solution with a vapor pressure of a standard solution. In an embodiment, the standard solution is contained in a cavity defined by a vapor-permeable membrane which is immersed in a specimen solution. The standard solution and the specimen solution are allowed to come into equilibrium by a movement of water vapor across the vapor-permeable membrane, which is permeable only to water vapor and not to any solutes or water itself. The movement of the water vapor between the standard solution and the specimen is measured by sensing a volume of water transferred between the standard solution and the specimen solution. A measurement of a volume change of the standard solution is made by sensing a change a conductivity of the standard solution. Alternatively, the volume change is determined by measuring a change in a photo-absorbance of the standard solution with a chromophore added therein. In yet another embodiment the volume change is determined by a direct visual measurement of the volume of the standard solution.
67 Citations
26 Claims
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1. An osmolarity sensor for measuring an osmolarity of a specimen solution, comprising:
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means for containing a standard solution including an aqueous solution of electrolytes; said means for containing defining a cavity, which is variable in volume, wherein the standard solution is held; said means for containing including a vapor-permeable membrane separating the standard solution from the specimen solution; said vapor-permeable membrane permitting passage of water vapor of the specimen solution and the standard solution, and blocking passage of solutes of said specimen solution; and means for sensing one of a conductivity and an absorbance of the standard solution, independent of positioning of said means for containing, and means, responsive to said means for sensing, for determining the osmolarity of the specimen solution when the standard solution has achieved substantial osmotic equilibrium with the specimen solution. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 26)
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13. An osmolarity sensor for measuring an osmolarity of a specimen solution, comprising:
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means for containing a standard solution including an aqueous solution of electorlytes; said means for containing defining a cavity wherein the standard solution is held; said means for containing including a vapor-permeable membrane separating the standard solution from the specimen solution; said vapor-permeable membrane permitting passage of water vapor of the specimen solution and the standard solution, and blocking passage of solutes of said specimen solution; and means for sensing one of a conductivity and an absorbance of the standard solution, independent of positioning of said means for containing, and means, responsive to said means for sensing, for determining the osmolarity of the specimen solution when the standard solution has achieved substantial osmotic equilibrium with the specimen solution. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An osmolarity sensor, for measuring an osmolarity of a specimen solution, comprising:
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means for containing a standard solution; said means for containing defining a cavity wherein the standard solution is held; said means for containing including a semipermeable membrane separating the standard solution from the specimen solution; said semipermeable membrane permitting passage of a solvent of the specimen solution and the standard solution and blocking passage of solutes of said specimen solution; and means for sensing one of a conductivity and an absorbance of the standard solution, independent of positioning of said means for containing, and means, responsive to said means for sensing, for determining the osmolarity of the specimen solution when the standard solution has achieved substantial osmotic equilibrium with the specimen solution. - View Dependent Claims (24, 25)
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Specification