Detection of Internal and External Methamphetamine in Human Hair by Ion Mobility Spectrometry

Internal and external methamphetamine (MA) was detected from human hair using ion mobility spectrometry (IMS). Direct IMS monitoring without any sample preparation proved to be effective only to detect MA from externally contaminated hair. The detection limit of external MA was 0.5 ng/mg by direct IMS monitoring when the sample amount was 1.0 mg. To detect MA incorporated in the hair, the authors measured MA users' hair samples by IMS after pulverization or digestion. Pulverized samples gave only moderate sensitivity for the detection of MA in the hair. Digestion of the hair sample with 5 M NaOH (methanol-water, 4 : 1) prior to IMS measurement was very effective to identify MA incorporated in the hair, and the drug was semi-quantitatively detected by this method. The detection limit of MA was 0.5 ng/mg with 2.0 mg of hair sample. Using a combination of the digestion method and direct IMS monitoring, the authors were able to distinguish between MA externally contaminating hair and MA incorporated in a user's hair. It was demonstrated using MA users' hair samples that the results obtained by the digestion method were in good agreement with the GC-MS results. Our method was also successfully applied to a limited amount of MA user's hair sample.