The analysis of methylamphetamine and para-hydroxy-methylamphetamine in post-mortem hair samples using liquid chromatography-tandem mass spectrometry.

External contamination is a well-recognized limitation of hair analysis for drugs of abuse like methylamphetamine (MA), and there are no guidelines regarding the analysis of specific metabolites of MA to assist interpretation. We developed an analytical method to detect MA, amphetamine (AMP), and para-hydroxy-methylamphetamine (p-OH-MA) in hair and present their concentrations among a cohort of deceased persons positive for MA in blood (n = 63). Hair samples (≤ 3 cm) were washed with dichloromethane and water prior to extraction using a methanolic micro-pulverization. The reconstituted hair extracts were separated on a UCT Selectra® Aqueous C18 HPLC Column (100 × 2.1 mm, 3 μm) by gradient elution and detected using a Sciex Triple Quad 6500+ system. Validation was satisfactory, and the lower limits of quantitation were 0.01 ng/mg for MA and AMP and 0.001 ng/mg for p-OH-MA. The median hair concentrations of MA, AMP, and p-OH-MA were 13 ng/mg (range = 0.015-49; n = 51), 1.1 ng/mg (range = 0.018-44; n = 60), and 0.020 ng/mg (range = 0.0012-0.38, n = 62), respectively. These concentrations in hair were strongly positively correlated (r = .7202 to .8641, p < .001), suggesting similar modes of incorporation. Moreover, the wash/hair ratios were indicative of external contamination, especially among the soiled group of hair samples. Therefore, further studies are necessary to determine concentrations of p-OH-MA in living MA users and confirm if this metabolite constitutes a potential marker of MA consumption.