Quantification of 4,4′-diaminodiphenylmethane by gas chromatography negative ion chemical lonization mass spectrometry

4,4′-Diaminodiphenylmethane (DDM) is an aromatic amine commonly used as a chemical intermediate in the production of isocyanates, polyurethanes, polymers, and elastomers. This compound is a carcinogen in laboratory animals, but no definitive data are available regarding its carcinogenicity in humans. On account of its diffusion and toxicity, specific analytical methods are required for monitoring human exposure to this compound. Methods for its quantification in biological fluids using gas chromatography-mass spectrometry (GC-MS) have been developed, using electron impact (EI) and negative ion chemical ionization (NICI). Here we described a GC-NICI-MS analytical procedure for DDM in acqueous matrices. A tetradeuterated analogue of DDM (DDM-d₄) was prepared in our laboratories with a simple proton-exchange reaction using deuterohydrochloric acid in deuterated methanol. This compound was used as internal standard. The samples were added with this internal standard, extracted with a solid phase column, and derivatized with a fluorinated anhydride. The final step was the GC-MS analysis of the resulting amide using the selected ion recording (SIR) mode. The use of NICI-MS as a GC detector gave high sensitivity, on account of the high response of the fluorinated species present in this type of ionization. Also, the EI ionization provided useful results and represents an alternative method. Furthermore, the accuracy of the method was guaranteed by the use of the deuterated internal Standard.