GC-MS Analysis of Acylated Derivatives of Methamphetamine and Regioisomeric Phenethylamines

Abstract

The analytical profiles are described for five amines : methamphetamine and four isomeric phenethylamines with a molecular weight of 149. These five amines contain an unsubstituted benzyl moiety and are regioisomeric within the imine fragment ; each shows a base peak in the electron impact mass spectrum at m/z 58. Furthermore, these compounds show similar gas chromatographic retention properties on methylsilicone (HP-1) and phenylmethylsilicone (HP-5) stationary phases. Thus, without reference standards it would be difficult to specifically differentiate methamphetamine from the other isomeric amines. The four primary and secondary amines are acylated with acetyl-, trifluoroacetyl-, pentafluoropropionyl-, heptafluorobutyryl- and 4-carbethoxyhexafluorobutyryl- groups in an effort to obtain more specific structural information from mass spectrometry and improve chromatographic resolution. The pentafluoropropionyl amide derivatives provide adequate GC resolution and mass spectra that can be used to differentiate among these regioisomeric amines. The underivatized amines show different R-values in TLC drug screening procedures but very similar responses to all visualization reagents. Cross-reactivity is observed in drug screening methods based upon immunoassay methods for the four primary and secondary amines.