Differences in binding affinities of MDA, MDMA, MDEA, Amphetamine, Methamphetamine, and their deuterated analogues to solid-phase extraction cartridges.
This study evaluated the potential for partial separation of drugs from their deuterated internal standards using Cerex(®) Polycrom™ CLIN II solid-phase extraction (SPE) cartridges. After elution from the column and derivatization, gas chromatography-mass spectrometry results showed that the target compound eluted from the SPE cartridge prior to its deuterated form. This elution separation effect was greater for 3,4-methylenedioxymethamphetamine (MDMA) and methamphetamine (MAMP) than for the other drugs studied. When the drugs were eluted in 0.5 mL increments from a 50 mg sorbent bed, no drug appeared in the first fraction. The drug to internal standard ratios (expected value 1.00) for subsequent fractions collected were 1.30, 1.07, and 0.83 for MDAMDA-d(5) 1.65, 1.18, 0.67, and 0.56 for MDMAMDMAd(5) and 1.37, 1.18, and 0.95 for MDEAMDEA-d(6). For d-AMP and d-MAMP, the expected ratio was 0.40. The subsequent ratios were 0.63, 0.46, 0.35, and 0.34 for d-AMPd-AMP-d(11) and 1.00, 0.59, 0.25, and 0.18 for d-MAMPd-MAMP-d(14). The affinity of d-MAMPd(14) was shown to be greater than that of d-MAMP-d(5), and deuteration at the propyl end of the molecule was shown to increase binding more than deuteration on the phenyl group.