Method and apparatus for determining liquid volume
View Patent ↗A method, apparatus and kit for precisely and accurately determining the volume of a liquid aliquot which can be used to calibrate a liquid delivery device. Two dye-containing solutions, a sample solution and a diluent solution, are prepared such that each solution contains a different dye, with the solutions having different absorbance values at a first wavelength and at a second wavelength. The absorbance value of a known volume of diluent solution is measured at both wavelengths. Either one aliquot of sample solution is added to the diluent solution and then absorbance measurements are made at both wavelengths, or multiple aliquots of sample solution are mixed serially into the diluent solution and then absorbance measurements are made at both wavelengths after each aliquot is added. The volume of any single aliquot is calculated by using a two-step formula which is based on the Beer-Lambert law.
1. A method for determining the volume of a liquid aliquot, comprising the steps of:
a. making a sample solution by adding a first dye to a solvent, the first dye having an extinction coefficient such that the sample solution has an absorbance value at a first wavelength which is different from an absorbance value at a second wavelength, wherein the sample solution made includes no other dye;
b. making a diluent solution by adding a second dye to a solvent, the second dye having an extinction coefficient such that the diluent solution has an absorbance value at the first wavelength which is different from an absorbance value at the second wavelength, wherein the second dye is different from the first dye and wherein the diluent solution made includes no other dye;
c. measuring the absorbance value of a known volume of the diluent solution at the first wavelength and at the second wavelength;
d. adding an aliquot of the sample solution containing the first dye only to the known volume of diluent solution of step (c) to make a sample-diluent solution;
e. measuring the absorbance value of the sample-diluent solution of step (d) at the first wavelength and at the second wavelength; and
f. calculating the volume of the aliquot of the sample solution by using the absorbance values measured in step (c) and step (e).
2. The method of claim 1 wherein after step (e) is performed, steps (d) and (e) are repeated successively at least one more time before step (f) is performed at least one time.
3. The method of claim 1 wherein after step (f) is performed, steps (d)-(f) are repeated successively n times, where n is greater than or equal to 1.
4. The method of claim 1 wherein step (f) is performed by using computer-executable software stored on a computer-readable medium, the computer-executable software being capable of calculating volume of a liquid sample solution aliquot based upon absorbance values measured by using the method.
5. The method of claim 1 wherein step (f) includes the step of calculating total volume using the equation:
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6. The method of claim 5 wherein step (f) further includes the step of calculating the aliquot volume using the equation:
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7. The method of claim 1 wherein the temperature of the diluent solution of step (c) is measured before step (c) is performed, and the temperature of the sample-diluent solution is measured before step (e) is performed.
8. The method of claim 7 wherein the temperature of either or both of the diluent solution and the sample-diluent solution are used in the calculation in step (f).