Determination of extractable methylene dianiline in thermoplastic polyurethanes by HPLC

Polyurethanes are finding increasing utilization in biomedical applications. Recently, the reported finding of methylene dianiline (4,4'-diaminodiphenylmethane, MDA) in the aqueous extracts of autoclaved 4,4'-diphenylmethane diisocyanate-based polyurethanes promoted our investigation of the origin and extent of extractable methylene dianiline in polyurethanes. A high-pressure liquid chromatography procedure using precolumn derivatization is utilized to selectively monitor the appearance of this diamine in the aqueous extracts of polyurethanes subjected to water immersion, heat aging, and various sterilization techniques. No MDA was found in the aqueous extracts of the treated polyurethane except for the case of prolonged steam autoclaving. The appearance of 3-5 ppb MDA in the extract under these conditions is attributed to hydrolysis of the polymer. The stability of the polyurethanes under most conditions renders these materials useful in biomedical applications.