Rapid quantitative chiral amphetamines liquid chromatography-tandem mass spectrometry: Method in plasma and oral fluid with a cost-effective chiral derivatizing reagent

Methamphetamine is a widely abused psychostimulant containing a chiral center. Consumption of over-the-counter and prescription medications may yield positive amphetamines results, but chiral separation of L- and D-methamphetamine and its metabolite amphetamine can help determine whether the source was licit or illicit. We present the first LC-MS/MS method with precolumn derivatization for methamphetamine and amphetamine chiral resolution in plasma and oral fluid collected with the Oral-Eze (R) and Quantisal (TM) devices. To 0.5 mL plasma, 0.75 mL Oral-Eze, or 1 mL Quantisal specimen racemic d(11)-methamphetamine and amphetamine internal standards were added, followed by protein precipitation. Samples were centrifuged and supernatants loaded onto pre-conditioned Phenomenex (R) Strata (TM)-XC Polymeric Strong Cation solid phase extraction columns. After washing, analytes were eluted with 5% ammonium hydroxide in methanol. The eluate was evaporated to dryness and reconstituted in water. Derivatization was performed with 1-fluoro-2,4-dinitrophenyl-5-L-alanineamide (Marfey's reagent) and heating at 45 degrees C for 1 h. Derivatized enantiomer separations were performed under isocratic conditions (methanol:water, 60:40) with a Phenomenex (R) Kinetex (R) 2.6 mu m C18 column. Analytes were identified and quantified by two MRM transitions and their ratio on a 3200 QTrap (AB Sciex) mass spectrometer in ESI negative mode. In all three matrices, the method was linear for all enantiomers from 1 to 500 mu g/L, with imprecision and accuracy of <= 11.3% and 853-108%, respectively. Extraction efficiencies ranged from 67.4 to 117% and matrix effects from -17.0 to 468%, with variation always <= 19.1%. Authentic plasma and OF specimens were collected from an IRB-approved study that included controlled Vicks (R) VapoInhaler (TM) administration. The present method is sensitive, selective, economic and rapid (separations accomplished in <10 min), and improves methamphetamine result interpretation. Published by Elsevier B.V.