Preparation of 4,4'-diaminodiphenylmethane-(2H4) for use as internal standard in the quantification of 4,4'-diaminodiphenylmethane

A simple method has been developed for the synthesis of 4,4'-diaminodiphenylmethane-(²H₄) for analytical purposes in gas chromatography-negative ion chemical ionization mass spectrometry (GC-NICIMS). It consists in a proton-deuterium exchange reaction of the diamine using deutero-hydrochloric acid in deuterated methanol. The reaction was conducted at 60°C. Deuteration of the diamine in the ortho positions of the aromatic rings was observed after eight days in these conditions, using mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy.