Spectroscopic characterization of 4-methylamphetamine: formaldehyde adduct formation hindered the identification by mass spectrometry

A powder was submitted to the author’s laboratory for analysis on the presence of illegal drugs. Based on the structure elucidation performed by nuclear nuclear magnetic resonance spectroscopy and analysis of the trimethylsilyl and trifluoroacetyl derivatives with gas chromatography mass spectrometry, the powder was found to contain the designer drugs 4-methylamphetamine, besides amphetamine and caffeine. The electron impact mass spectrum of 4-methylamphetamine obtained from the analysis of a methanolic sample solution showed a base ion of m/z 56 rather than the expected m/z 44, therefore no hit was found with an electron impact mass spectrum present in the mass spectral library and literature. The increase of 12 atomic mass units was explained by formaldehyde-adduct formation.