Calibration method for water hardness measurement
First Claim
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1. A method of calibrating a fluorescence-measuring instrument for soluble magnesium, the method comprising:
- measuring background fluorescence of a low calibration standard solution comprising soluble magnesium at a known concentration;
combining a magnesium-reactant solution comprising an inert fluorescing agent at a known concentration and a magnesium coordinating fluorescing reagent with the low calibration standard solution, thereby forming a combined low calibration standard solution comprising the inert fluorescing agent and a coordinated magnesium compound;
measuring fluorometric responses of the inert fluorescing agent and the coordinated magnesium compound in the combined low calibration standard solution;
measuring fluorometric response of an inert fluorescing agent in a high calibration standard solution comprising both soluble magnesium and inert fluorescing agent at known concentrations;
combining the magnesium-reactant solution with the high calibration standard solution, thereby forming a combined high calibration standard solution comprising inert fluorescing agent and a coordinated magnesium compound;
measuring fluorometric responses of the inert fluorescing agent and the coordinated magnesium compound in the combined high calibration standard solution; and
calibrating the fluorescence-measuring instrument based on the measured fluorometric responses and the known concentrations of soluble magnesium and inert fluorescing agent in the low calibration standard solution and in the high calibration standard solution.
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Abstract
Disclosed are methods that can be used to automatically calibrate a fluorescence-measuring instrument capable of continuously measuring the concentration of hardness in process water. The calibration method is used to compensate for drift of instrument and equipment, changes of operational conditions, and contamination of reagents and calibration standards. Calibration of the fluorescence-measuring instrument using the present calibration method improves both accuracy and repeatability for subsequent hardness concentration measurements.
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Citations
20 Claims
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1. A method of calibrating a fluorescence-measuring instrument for soluble magnesium, the method comprising:
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measuring background fluorescence of a low calibration standard solution comprising soluble magnesium at a known concentration; combining a magnesium-reactant solution comprising an inert fluorescing agent at a known concentration and a magnesium coordinating fluorescing reagent with the low calibration standard solution, thereby forming a combined low calibration standard solution comprising the inert fluorescing agent and a coordinated magnesium compound; measuring fluorometric responses of the inert fluorescing agent and the coordinated magnesium compound in the combined low calibration standard solution; measuring fluorometric response of an inert fluorescing agent in a high calibration standard solution comprising both soluble magnesium and inert fluorescing agent at known concentrations; combining the magnesium-reactant solution with the high calibration standard solution, thereby forming a combined high calibration standard solution comprising inert fluorescing agent and a coordinated magnesium compound; measuring fluorometric responses of the inert fluorescing agent and the coordinated magnesium compound in the combined high calibration standard solution; and calibrating the fluorescence-measuring instrument based on the measured fluorometric responses and the known concentrations of soluble magnesium and inert fluorescing agent in the low calibration standard solution and in the high calibration standard solution. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of calibrating a fluorescence-measuring instrument for soluble magnesium and total hardness, the method comprising:
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measuring background fluorescence of a low calibration standard solution comprising soluble magnesium and soluble calcium each at known concentrations; combining a magnesium-reactant solution comprising an inert fluorescing agent at a known concentration and a magnesium coordinating fluorescing reagent with the low calibration standard solution, thereby forming a combined low calibration standard solution comprising the inert fluorescing agent and a coordinated magnesium compound; measuring fluorometric responses of the inert fluorescing agent and the coordinated magnesium compound in the combined low calibration standard solution; combining the magnesium-reactant solution and a total hardness-reactant solution comprising a magnesium-containing reagent with the low calibration standard solution, thereby forming a calcium-displaced low calibration standard solution comprising the inert fluorescing agent and the coordinated magnesium compound; measuring fluorometric responses of the inert fluorescing agent and the coordinated magnesium compound in the calcium-displaced low calibration standard solution in order to measure total hardness; measuring fluorometric response of an inert fluorescing agent in a high calibration standard solution comprising soluble magnesium, soluble calcium, and the inert fluorescing agent, each at known concentrations; combining the magnesium-reactant solution with the high calibration standard solution, thereby forming a combined high calibration standard solution comprising the inert fluorescing agent and a coordinated magnesium compound; measuring fluorometric responses of the inert fluorescing agent and the coordinated magnesium compound in the combined high calibration standard solution; combining the magnesium-reactant solution and the total hardness-reactant solution with the high calibration standard solution, thereby forming a calcium-displaced high calibration standard solution comprising the inert fluorescing agent and the coordinated magnesium compound; measuring fluorometric responses of the inert fluorescing agent and the coordinated magnesium compound in the calcium-displaced high calibration standard solution in order to measure total hardness; and calibrating the fluorescence-measuring instrument based on the measured fluorometric responses, the known concentrations of soluble magnesium and inert fluorescing agent, and the measurements of total hardness in the low calibration standard solution and in the high calibration standard solution. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification