Patent ID: 8679850

Claim:
A method of determining a concentration of residual cationic polymers present at less than 1 ppm in a target water sample, said method comprising: adding a polymer dispersant solution and a phosphate solution to said target water sample, wherein: said polymer dispersant solution comprises calcium hardness and at least one calcium phosphate inhibition polymer dispersant therein and wherein said polymer dispersant is selected from the group consisting of acrylic acid/2-hydroxypropylacrylate copolymers, acrylic acid/1-allyloxy-2-hydroxypropylsulfonic acid copolymers, acrylic acid/polyethyleneglycol monoallyl ether sulfate/1-allyoxy-2-hydroxypropylsulfonic acid terpolymers, and combinations thereof; and wherein said phosphate solution comprises at least one phosphate therein; standing said target water sample for about 1-15 minutes to allow the formation of calcium phosphate; measuring a turbidity of said target water sample produced by said calcium phosphate; and comparing said turbidity of said target water sample with a turbidity calibration curve of samples containing known concentrations of cationic polymers to determine a concentration of said residual cationic polymers in said target water sample.