Method for monitoring and in-system concentration control of polyelectrolyte using fluorochromatic dye

PURPOSE: To provide a method for monitoring and in-system concentration control of an aqueous polyelectrolyte with a fluorochromatic dye, and more specifically, for monitoring and/or control of reduction in concentration and/or dosage of the polyelectrolyte by which a substantially linear response to the polyelectrolyte concentration can be obtained irrespectively of experimental skill of a worker. CONSTITUTION: This monitoring and/or control method of the polyelectrolyte concentration in water of an aqueous system comprises: withdrawing a sample of the water; adding a known or standard amount of a fluorochromatic reagent to the sample; then directing light energy into the sample so that light energy of a selected excitation wavelength for the fluorochromatic dye is available for absorption by the fluorochromatic reagent; measuring the intensity of light emitted about a selected emission wavelength for the fluorochromatic reagent; comparing the intensity of the emitted light to a standard curve which comprises a plot of fluorescence emission intensity of the fluorochromatic reagent in the presence of a polyelectrolyte versus concentration of the polyelectrolyte; and determining the concentration of the polyelectrolyte in the water sample from the comparison.