Potential of chromatography and mass spectrometry for the differentiation of three series of positional isomers of 2-(dimethoxyphenyl)-N-(2-halogenobenzyl)ethanamines.

N-(2-substituted benzyl)-2,5-dimethoxyphenethylamines often cause severe poisonings which has led to their legal prohibition in many countries. At the same time, their positional isomers can be studied as potential therapeutic drugs. In this regard, the search for various approaches to differentiate these isomers is an important practical task, the solution of which would guarantee from identification errors during laboratory analysis. In this paper, the possibilities of differentiation of isomers varying in the position of two methoxy groups in the phenylethyl part of the molecule are considered on the example of compounds of NBF, NBCl, and NBBr series by chromatography-mass spectrometry methods. Gas or liquid reverse-phase chromatography in the proposed chromatographic separation modes has demonstrated their ability to resolve this problem reliably. Data on retention indices of isomeric compounds and their derivatives can serve as an additional identification criterion for gas chromatography-mass spectrometry (GC-MS) analysis. Differentiation of NBF and NBCl isomers using electron ionization (EI) mass spectra is feasible only if both the spectrum of the compound and its N-trifluoroacetyl derivative are registered; differentiation of NBBr positional isomers under these conditions does not require obtaining the derivatives. Using electrospray ion source, the compounds can easily be differentiated based on the distinctive features of their collision induced dissociation (CID) spectra recorded at low energy values, which also does not require the synthesis of derivatives. The data presented in current paper will be useful for analysis in laboratories providing the determination of narcotic drugs.