[Identification of optical isomers of methamphetamine and its application to forensic medicine]

In order to identify optical isomers (d and l-) of methamphetamine (MAMP), GC-MS analysis using optically resolvable reagent of N-trifluoroacetyl-L-prolyl chloride (L-TPC) and HPLC analysis using chiral cellulose-based columns were compared. In analysis of d- or l-MAMP (M) of TPC (T) derivatives by the GC-MS, contrary to the expectation that only d(M)-L(T) or l(M)-L(T) could be detected chemically, two diastereomers of d(M)-L(T) and d(M)-D(T) for d-MAMP and two of l(M)-L(T) and l(M)-D(T) for l-MAMP were demonstrated respectively. This results was attributed to a small percentage of D-TPC present in L-TPC. For racemic (dl)-MAMP, none of these four isomers could be individually isolated, and they were detected as two overlapping peaks. In the HPLC analysis using chiral columns, d- and l-isomers of MAMP and amphetamine (AMP) could be clearly isolated with merely one analytical procedure, and the l/d ratio was possible to calculate with facility. From the rats urine administered d- or l-MAMP, only the corresponded optically active form of the administered drug was detected, and when racemic (dl)-MAMP was administered, d-MAMP, l-MAMP and their metabolites AMP were distinctly detected. The l/d ratio calculated from amount of MAMP and AMP excreted in rat urine within 24 hr was not in accordance with that of the administered dl-MAMP (l/d = 1.01): the l/d ratio was 0.45 for MAMP and 0.58 for AMP, and 0.50 for the total of MAMP and AMP. The similar results were observed in case of racemic (dl)-AMP. From several human specimens obtained from the cadavers dead by MAMP poisoning, only d-MAMP and the metabolite d-AMP were detected, and neither l-MAMP or l-AMP were demonstrated. In particular, a high concentration of d-MAMP was detected in gastric contents, brain, lung and liver. From the MAMP powder in possession, only d-MAMP was detected. These results suggest that this chiral column-HPLC procedure could be applied to medicolegal practice and forensic scientific investigation.