The invention provides a method for measuring the concentration of anionic polymers in an industrial water system. Specifically, the concentration of anionic polymer can be measured by combining an indicator dye composition that includes an acridine compound or a salt thereof to a water sample and measuring the absorbance of the mixture. The concentration can be determined by comparing the absorbance of the mixture to absorbance values on a pre-determined calibration curve. The dosage of anionic polymer can be optionally adjusted based on the concentration.