Size exclusion chromatography [or gel permeation chromatography ( GPC ) ] has been suggested in the past for the analysis of oligomers.'?' Highpressure liquid chromatography (HPLC) was used in a brief study of the kinetics of polyurethane polymeri~ ationF.~u rukawa and Yokoyama4 described the analysis of polyurethane prepolymers by GPC after derivatizing with methanol. Their study succeeded in only partially separating the various oligomers in the prepolymer and the derivatization reaction required several hours to complete. Their work briefly studied the composition of polyurethane prepolymer mixtures formed with several different stoichiometries. Papazian5 achieved partial separation of the reaction products from excess aliphatic diisocyanate and trimethylol propane. No conclusions were drawn regarding the polyurethane reaction conditions. In none of these studies was a capping agent selected so as to enhance the sensitivity of the detection.