Selective extraction of BPA in milk analysis by capillary electrophoresis using a chemically modified molecularly imprinted polymer

Bisphenol A (BPA) is an endocrine disrupting compound commonly found in consumer plastic goods. For environmental and food analyses, however, selective extraction of BPA in the presence of other organic compounds will be challenging unless a molecularly imprinted polymer (MIP) is commercially available. An MIP was prepared in our lab using BPA as a template, ethylene glycol dimethacrylate as a cross-linking monomer and methacrylic acid as a functional co-monomer. Non-specific binding sites in the MIP were blocked by site-selective chemical modification with diazomethane to form a treated molecularly imprinted polymer (TMIP). Water and milk samples were spiked with BPA as well as zwitterionic, negatively and positively charged pharmaceutical and other compounds for binding tests. Unlike high-performance liquid chromatography, capillary electrophoresis (CE) demonstrated the ability to analyze milk samples after dilution with a background electrolyte. BPA was easily separated from all milk constituents on the basis of different electrophoretic mobility values. Repeatedly, CE binding test results demonstrated that the TMIP afforded superior selectivity than a commercial MIP.