Chiral LC/MS Analysis of Methamphetamine in Urine on Astec® CHIROBIOTIC® V2

Differentiation of Illicit D-Methamphetamine from Over-the-Counter L-Methamphetamine by LC-MS Contributed Article

Introduction

Methamphetamine (Figure 1) is a powerful stimulant, often used as a recreational drug of abuse or as a doping agent in sports. Its presence in urine is screened for by enzymatic immunoassays and confirmed using a hyphenated mass spectrometry chromatographic method. However, this molecule exists in two enantiomeric forms, L-methamphetamine (or levo-methamphetamine), a vasoconstrictor used in the formulation of over-the-counter medications such as Vicks^® Vapor Inhaler and D-Methamphetamine, the illicit stimulant.¹ Immunoassay does not differentiate between the legal and illicit versions and therefore will report a positive finding if either are detected in the specimen above cutoff concentrations. The same holds true for reverse-phase LC-MS techniques that are commonly used in toxicology for drug of abuse quantitation.

This poses a problem when analyzing specimens from patients who are using the legal decongestants or medications such as selegiline and fenproporex, which may metabolize to methamphetamine². To confirm which molecule is present in a specimen testing positive by immunoassay for methamphetamine, a chiral LC-MS method was developed using an Astec CHIROBIOTIC V2 HPLC column. The method was applied to real patient samples allowing such differentiation with an extremely high level of accuracy.