A method was developed for the determination of residual monomers, bisphenol A (BPA) and diphenylcarbonate, and polymerization regulators, phenol, 4-tert-butylphenol and 4-(1, 1, 3, 3-tetramethylbutyl) phenol in polycarbonate (PC) by high performance liquid chromatography using a reversed-phase column and an ultraviolet (UV) detector.
PC resin was dissolved in dichloromethane and polymers were precipitated with acetone. The clear upper layer was taken and evaporated. The concentrate was dissolved in acetonitrile and water was added to precipitate oligomers. Monomers and polymerization regulators were separated by a linear gradient method using an acetonitrile-water mixture as a mobile phase. The monomers and polymerization regulators were detected by absorbance measurement at 217nm. The detection limit for each compound was 2ppm in PC resin or products. The recoveries of the five compounds were more than 90%.
The proposed method was applied to the analysis of three kinds of commercial products, three types of polymer pellets and one type of polymer sheet. BPA and 4-tert-butylphenol were observed in all samples, and phenol was detected in only one sample. The residual amounts of BPA, phenol and 4-tert-butylphenol in the teacup were 116ppm, 19ppm and 36ppm, respectively. BPA in the teacup migrated into 20% ethanol (60°C for 30min) to a concentration of 0.005ppm.