Strategies for Identifying Amphetamine and Methamphetamine Derivatives in Urine by Gas Chromatography-Mass Spectrometry

Abstract

Introduction: One of the challenges in doping control analysis is to demonstrate the preciseness and accuracy of the analytical results. Therefore, it is necessary to show evidence during the analysis of the samples about what exactly the athlete consumed. Selegiline is a stimulant substance synthesized from levo-methamphetamine. Its fundamental metabolites are L-amphetamine and L-methamphetamine which are also metabolites of other substances.

Objective: To evaluate the formation of derivatives in the analysis of amphetamine and methamphetamine through three chromatographic parameters to establish a strategy for the identification of both compounds.

Methods: Urine samples collected before and after oral administration of 10 mg of selegiline were evaluated to verify the functionality of the methods. After a liquid-liquid extraction with tert-butyl methylether at alkaline pH, R-α-methoxy-α-(trifluoromethyl)-phenylacetyl (R-MTPCl) and N-trifluoroacetamide (TFA) derivatives were obtained for analysis by gas chromatography-mass spectrometry. The outcomes without and with formation of N-TFA and R-MTPCl derivatives were compared.

Results: N-TFA derivatives proved not to be a good option in quantification trials due to the formation of multiple derivatives. However, its application in identification processes (like the derivative R-MTPCl) allowed the obtention of fragments of high diagnostic value in the mass spectrum. After elimination of specific metabolites of selegiline, only amphetamine and methamphetamine were observed. The use of the derivative R-MTPCl chromatographically resolved the levo and dextro enantiomers of both compounds.

Conclusions: The evaluation of samples containing amphetamine and methamphetamine-N-TFA allowed to obtain mass spectra with high diagnostic value, but it is not recommended in quantification tests. The use of the R-MTPCl reagent increased the accuracy in the identification of the original selegiline drug.