2,3-Methylenedioxy Regioisomer of 3,4-MDMA
(Rated as: excellent)
Differentiation of the 2,3-Methylenedioxy Regioisomer of 3,4-MDMA (Ecstasy) by GC/MS
Journal of Analytical Toxicology, Volume 26, Number 7, October 2002, pp. 537-539
3,4-Methylenedioxymethamphetamine (MDMA) is a commonly abused drug that has had a significant increase in popularity over the past few years. This drug, which goes by a number of common names (such as Ecstasy, XTC, X, Adam, etc.), is only one of several isomers. 2,3-MDMA is an aromatic positional isomer of 3,4-MDMA (Figure 1).
Several studies have reported methods for the identification of ring and side chain (1–5) regioisomers of MDMA. These studies primarily dealt with the testing of confiscated drug material to support criminal prosecution for the possession, synthesis, or sale of a controlled substance. The ability to unequivocally demonstrate the compound that is present is important in legal proceedings. Since the passage of the Controlled Substances Analogue Act of 1986, all analogues are considered, for purposes of law, to be in Schedule I unless they are otherwise scheduled. Despite this fact, legal requirements demand that the charges be specific and that forensic scientists be able to demonstrate that the charge is correct with respect to the drug involved, thus driving the need for the studies. These legal requirements apply equally to the identification of the drug in confiscated materials or when isolated from biological samples. Published studies do not describe the behavior of the regioisomers under conditions commonly used for the analysis of biological samples, but focus on the drug material itself, a situation addressed by the current report.
Recently, Borth et al. (1) reported differentiation of ring-substituted phenylalkylamines including 2,3- and 3,4-MDMA using gas chromatography with tandem mass spectrometry (GC–MS–MS). Using the power of MS–MS, this group was able to demonstrate a significant difference in the product ion spectra of 2,3- and 3,4-methylenedioxy compounds with electron and chemical ionization. Casale et al. (2) described the synthesis and characterization of 2,3-methylenedioxyamphetamines (MDA) using infrared (IR), nuclear magnetic resonance spectroscopy, GC, and MS. Their study showed the mass spectra of underivatized 2,3- and 3,4-MDMA to be quite similar. Both spectra had ions at m/z 135, but the 2,3-MDMA showed the presence of an ion of substantial intensity at m/z 136 whereas the 3,4-MDMA had an m/z 136 peak of much lower intensity. The compounds also eluted at different times from a 30-m DB-1 GC column. Soine et al. described the differentiation of 2,3- and 3,4-MDA using thin-layer chromatography, IR, UV, MS, and GC. GC was successful in separating the two compounds using 5% OV-7 and 10% OV-1 columns. These data were also generated using underivatized compounds (5). Another study by Soine et al. evaluated GC–IR-MS for the differentiation of a variety of side-chain and ring-substituted amphetamines (3). The ring and side-chain regioisomers of MDMA were also studied by Aalberg et al. (4) using liquid chromatography (LC) and GC–MS. Consistent with previous reports, this study showed very similar mass spectra and demonstrated the ability to separate the underivatized compounds by GC and LC.
The purpose of this study was to determine whether 2,3-MDMA posed a potential problem for the proper identification of 3,4-MDMA or could be confused for the latter using routine analytical procedures employed in drug testing laboratories.
Following liquid–liquid extraction and derivatization with heptafluorobutyric anhydride, 2,3- and 3,4-MDMA, along with 3,4-MDA, were analyzed using an HP-1 capillary GC column (12-m, 0.20-mm i.d., 0.33-µm film thickness).
The GC conditions included the set injector and interface temperatures of 270°C, and the oven temperature was programmed from 80°C for 1.00 min to 280°C at 20°C/min. This procedure is routinely used for the analysis of MDA, MDMA, and methylenedioxyethylamphetamine from biological samples in our laboratory using a Hewlett-Packard 6890 GC coupled with an HP 5973 MS using a 7683 autoinjector. In the current experiments, full-scan mass spectra were obtained by scanning from m/z 50–500. All prominent ions in the MDMA spectra were monitored using the selected-ion monitoring mode (m/z 135, 162, 210, 254, and 389), and their ratios were determined and compared using data from six replicate injections for each derivatized compound.
Each of these compounds were well separated chromatographically. Figure 2 shows an example of the chromatography of the HFB derivatives of 3,4-MDA, 3,4-MDMA, and 2,3-MDMA. Under the conditions described, the retention times of the HFB derivatives were 5.46 min for 3,4-MDA, 5.73 min for 2,3-MDMA, and 6.02 min for 3,4-MDMA. The separation appeared to be sufficient to avoid peak overlap even at the high concentrations (short of saturation) of some of the analytes. The mass spectra of both derivatized MDMA isomers gave the same major fragment ions at m/z 389, 254, 210, 162, and 135 (Figure 3). The ratios between the major ions are significantly different with respect to the of m/z 135 and 162 compared with m/z 254 (p < 0.00000000003; ANOVA, SPSS version 10.1). Ratios at m/z 210 were closer but still showed a statistically significant difference (p < 0.00000002); however, the review of the data showed that it is possible for the 2,3-MDMA to produce an ion ratio that would fall within the lower limit of the ± 20% range of the 254:210 ratio of 3,4-MDMA. The 254:389 ion ratio was not significantly different (p = 0.098) between the two compounds (Table I).
It is clear from the data in this report that the derivatized 2,3-MDMA is easily separated from its more common regioisomer 3,4-MDMA under commonly used derivatization and chromatographic conditions. Even though the compounds share the same prominent ions, chromatographic resolution eliminates any potential interference.
Thanks to Dr. C. Randall Clark for the 2,3-MDMA used in this study and to Dr. Mel Kaufman and Dr. Arvind Modak for interesting discussions regarding 2,3-MDMA.
1. S. Borth, W. Hansel, T. Junge, and P. Rosner. Regioisomenc differentiation of 2,3- and 3,4-methylenedioxy ring-substituted phenylalkylamines by gas chromatography/tandem mass spectrometry. J. Mass Spectrom. 35(6): 705–710 (2000).
2. J.F. Casale, P.A. Hays, and R.F.X. Klein. Synthesis and characterization of the 2,3-MDAs. J. Forensic Sci. 40(3): 391–400 (1995).
3. W.H. Soine, W. Duncan, R. Lambert, R. Middleberg, H. Finley, and D.J. O’Neil. Differentiation of side chain isomers of ring-substituted amphetamines using gas chromatography/infrared/mass spectrometry (GC/IR/MS). J. Forensic Sci. 37(2): 513–527 (1992).
4. L. Aalberg, J. DeRuiter, F.T. Noggle, E. Sippola, and C.R. Clark. Chromatographic and mass spectral methods of identification for the side-chain and ring regioisomers of methylenedioxymethamphetamine. J. Chromatogr. Sci. 38: 329–337 (2000).
5. W.H. Soine, R.E. Shark, and W.H. Agee. Differentiation of 2,3-MDA from 3,4-MDA. J. Forensic Sci. 28(2): 386–390 (1983)..