RP-LC Determination of Residual Monomers in Polycarboxylate Superplasticizers

A procedure was developed for the determination of residual monomers in polycarboxylate superplasticizer by reversed-phase high performance liquid chromatography. Seven kinds of residual monomers were quantitatively determined on a SinoChrom ODS-BP (C18) column and UV detector at 205 nm. The mobile phases which were used to determine micromolecular monomers were composed of acetonitrile and phosphate buffer solution (0.05 mol L(-1), pH = 3) in the ratio of 8:92 (v/v). While the mobile phases for long side-chain monomers testing were composed of acetonitrile and phosphate buffer solution (0.05 mol L(-1), pH = 6.5) in the ratio of 40:60 (v/v). The linear response ranged from 4.0 x 10(-6)-2.0 x 10(-3) mol L(-1). The detection limit was 0.12 x 10(-5)-0.8 x 10(-5) mol L(-1). Determination of real samples showed that relative standard deviation of high conversion rate samples was 3.1-8.7% and standard addition recovery ratio was 91.5-102.8%. While the relative standard deviation of low conversion rate samples was less than or close to 1% and the standard addition recovery ratio was 96.3-103.1%.