Determination of ethoxylated bisphenol A dimethacrylate monomers in dental composites by micellar electrokinetic chromatography.

Separation of monomeric constituents of ethoxylated bisphenol A (BIS-EMA) with between 2 and 15 ethoxy groups per phenol in the molecule was investigated with micellar electrokinetic chromatography at different volume percentages methanol in the background electrolyte (10 mM sodium dodecylsulfate, 100 mM borate-50 mM phosphate buffer, pH 7.0). The conditions allowed the differentiation of the lower from the higher BIS-EMA homologues and of isomers, and enabled the characterisation of commercial dental composite materials. The decay curve for the light induced radical polymerisation of BIS-EMA in composite specimens was determined. The content of leachable monomers after light curing was quantified, resulting in 6% of the initial value after the recommended curing time. The method is suited to determine monomer constituents in polymerised composite material in the ppm range.