Summary The mass spectra of di-and polyamines containing a 1, 2-ethandiamine or a 1, 3- propandiamine unit are quite often characterized by [M+ 1 I]+-peaks. It is demonstrated that these peaks correspond to a fragment-ion formed by loss of H. from a formaldehyde- condensation product (eg 15) or by loss of CH,. from a acetaldehyde-condensation product (eg 16) with the diamine. The aldehydes are usually impurities in solvents (especially ...