Potentiometry of effective concentration of polyacrylate as scale inhibitor

The concentration of polyacrylate (PA) used as a scale inhibitor was potentiometrically determined with a solid state copper ion-selective electrode after addition of Cu2+ as a probe. While the conventional methods monitor only the total concentration of PA, the proposed method measures the free, “effective” concentration of PA in equilibrium with species like Ca2+ and CaCO3. The slope of a potential response to PA was −40 mV decade−1 and the limit of detection was 10−6.3 M (= mol dm−3) at a probe concentration of 10−6 M. The system could be used to control the PA concentration just enough to prevent the scale formation in various circulating water systems.