Abstract: A method of quantitatively detecting a polymer in a solution of the polymer in a solvent is provided, which method comprises the steps of (a) adding to the solution a non-solvent for said polymer in a sufficient amount to make the resulting liquid turbid and (b) measuring the turbidity of the resulting liquid. A detecting device for detecting a polymer in a polymer-containing solution is also provided, which device comprises a line for supplying polymer-containing solution, a line for supplying non-solvent, a mixing chamber, a line connected to said mixing chamber for conveying the mixed liquid, and a detector for measuring turbidity in the mixed liquid, as well as an HPLC apparatus comprising a liquid separation system, especially a Gradient Polymer Elution Chromatography (GPEC)® system, connected to said detecting device.