Enantiomeric Separation and Quantitation of ( )-Amphetamine, ( )-Methamphetamine, ( )-MDA, ( )-MDMA, and ( )-MDEA in Urine Specimens by GC-EI-MS after Derivatization with (R)-(-)- or (S)-(+)- -Methoxy- -(trifluoromethy)phenylacetyl Chloride (MTPA)
Journal of Analytical Toxicology September 1, 2004 Bindu D. Paul, John F. Jemionek, David Lesser et al. 46 citations
A new gas chromatography-mass spectrometry (GC-MS) method using (R)-(-)-alpha-methoxy-alpha-(trifluoromethyl)phenylacetyl chloride (MTPA) as a chiral derivatizing agent avoids racemization problems seen with the standard reagent (S)-(-)-trifluoroacetylprolyl chloride (TPC). The MTPA method reliably separates the (R)-(-)- and (S)-(+)-isomers of methamphetamine, amphetamine, MDA, MDMA, and MDEA. In 91% of methamphetamine-positive urine specimens, only the (S)-(+)-isomer—indicative of illicit use—was detected. For MDMA-positive specimens, (R)-(-)-isomer concentrations exceeded (S)-(+)-isomer, suggesting longer bodily retention of the (R)-(-)-form. Quantitation was linear over 25–10,000 ng/mL for most drugs, with correlation coefficients >0.996 and precision within ±11% at 500 ng/mL. The single MTPA method can replace two separate GC-MS tests needed to confirm illicit (S)-(+)-amphetamine and methamphetamine use.