Structural elucidation of tramadol, its derivatives, and metabolites using chemical derivatization and liquid chromatography–high‐resolution tandem mass spectrometry

Abstract

RationaleTramadol (T) is a strong painkiller drug that belongs to the opioid analgesic group. Several accidental intoxication cases after oral administration of T have been reported in the past decade. Tramadol, its derivatives, and metabolites present information‐limited mass spectra with one prominent peak representing the amine‐containing residue; therefore, their structural determination based on both electron impact mass spectrometry (EI‐MS) and ESI‐MS/MS spectra could be misleading.MethodsA novel analytical method for the structural elucidation of tramadol, its four homologs, and its two main phase I metabolites (N‐desmethyltramadol and O‐desmethyltramadol) was developed using chemical modification and liquid chromatography–high‐resolution tandem mass spectrometry (LC‐HR‐MS/MS) with Orbitrap technology.ResultsAfter chemical derivatization, each of the investigated T series exhibited informative mass spectra that enabled better exposition of their structures. The developed method was successfully implemented to explicitly identify the structures of tramadol and its N‐desmethyltramadol metabolite in urine samples at low ng/mL levels.ConclusionsAn efficient derivatization‐aided strategy was developed for rapidly elucidating the structure of tramadol‐like compounds. The method is intended to assist forensic chemists in better diagnosing T and its analogs and metabolites in clinical or forensic toxicology laboratories.