LC and GC—MS Analysis of 4-Bromo-2,5-Dimethoxyphenethylamine (Nexus) and 2-Propanamine and 2-Butanamine Analogues

The street drug Nexus (4-bromo-2,5-dimethoxyphenethylamine) has appeared in clandestine samples in recent years. This hallucinogenic phenethylamine is prepared from the commercially available aldehyde, 2,5-dimethoxybenzaldehyde, and other readily available precursor chemicals and reagents. Nexus and some designer analogues are separated by liquid chromatography using a C18 stationary phase and an acidic (pH 3) mobile phase. Nexus, a brominated phenethylamine, shows enhanced reversed-phase retention relative to the unbrominated precursor phenethylamine. The mass spectra of these amines show fragment ions consistent with amine-dominated reactions common to phenethylamines and substituted phenethylamines. The gas chromatographic—mass spectrometric analysis of mixtures of the amines and the synthetic precursor nitroethenes show on-column reaction products that complicate the analytical results. These reaction products are identified as the imines that result from condensation of the amine with the substituted benzaldehyde, which is generated from the 2-nitroethene.