Measurement of 3,4-MDMA and Related Amines in Diagnostic and Forensic Laboratories

Clinical Laboratory Science, Spring 2005 by Skrinska, Victor A, Gock, Susan B

FORENSICANALYSIS OF PSYCHOSTIMULANTS

Analysis of postmortem specimens for the presence of psychostimulants such as MDMA, MDEA, and MDA typically involves extraction of the drugs from tissues including liver, muscle, and brain as well as from urine, central blood, peripheral blood, and vitreous humor.45 Varying degrees of putrefaction and postmortem redistribution of drugs further complicate the analysis. While hair and urine are suitable forensic specimens to determine the presence of the drugs, peripheral blood and vitreous humor are reported to provide the best estimate of the blood concentration at the time of death.45-48

There are various analytical techniques available for initial screening, confirmation, and quantification of forensic specimens such as thin-layer chromatography (TLC), HPLC, and GC/MS.45-47 TLC is a common initial screening technique when a method capable of detecting a broad-spectrum of drugs in urine specimens is required. Identification is based on Rf value and the color characteristics following exposure to specific staining reagents. The Toxi-Lab A� system for the detection of basic and neutral drugs in urine specimens is able to differentiate sympathomimetic amines such as ephedrine, pseudoephedrine, and phenylpropanolamine from illicit dugs such as amphetamine, methamphetamine, MDMA, and MDA. Sensitivity for most of the drugs in this class using this procedure is approximately 500 ng/mL.

Immunoassays may also be applied to forensic drug screens for the presence of MDMA and related metabolites.30 However, as mentioned earlier, immunoassay techniques for the detection of amphetamine and methamphetamine have variable amounts of antibody cross reactivity to other structurally related sympathomimetic amines including pseudoephedrine and ephedrine.30 Antibody cross reactivity is variable and dependent on both the concentration of the structurally related analyte present in the specimen as well as the source of the antibodies used for detection. Higher levels of antibody cross reactivity occur with polyclonal antibody assays in comparison to monoclonal antibody assays. Monoclonal antibody assays are more specific and exhibit less cross-reactivity to structurally related compounds and should be used when high selectivity is desired. Application of immunoassay techniques for the analysis of postmortem specimens poses a problem due to decomposition occurring during the postmortem interval. This may result in the production of biogenic amines such as beta-phenethylamine or tyramine that have the potential to produce a false positive with amphetamine immunoassays due to the cross reactivity with these analytes. Due to the lack of specificity associated with immunoassays for identification of the specific psychostimulants present in the sample, confirmation of positive immunoassay results should be made using an alternate analytical methodology. GC/MS analysis with selective ion monitoring is the analytical methodology routinely utilized for drug confirmation and quantification. Derivatization of the drugs with heptafluorobutyric anhydride, pentafluoropropionic anhydride, or trifluoroacetic anhydride prior to analysis improves chromatographic behavior and reduces fragmentation so that higher mass fragments can be used for GC/MS selective ion monitoring which allows a more definitive identification and confirmation of the drugs.