Forensic Analysis of Drug Traces from Cotton Fabric
The increased use of methamphetamine has led to a variety of new manufacturing methods which expose both perpetrators and innocent people to significant amounts of the drug. Cotton fabric, in the form of clothing, is often present at the scene and can be contaminated with trace drug residue. The ability to detect these traces of drugs from fabric would allow law enforcement to determine who has been exposed to, or even manufactured, an illegal drug. In the present work, Direct Analysis in Real Time (DART) mass spectroscopy is used to measure traces of drugs on a patterned glass fiber membrane. Previous work showed that a disk of this membrane absorbs over half of the liquid applied to cotton fabric, and that large signals from the DART are obtained when the disk is mounted in front of the DART source using a custom-made holder fabricated from aluminum. New work determined a number of important operating conditions: 1) the half-life of methamphetamine desorption and ionization from the disks at DART source temperatures from 200-500°C which is important in optimizing the sample run time, and 2) the effect of pattern design on the analytical signal. In addition, extraction and semi-quantitation of low levels of methamphetamine (5 µg) from cotton cloth was demonstrated using an internal standard added to a drop of solution added to the cotton fabric, followed by application of the disk and measurement by DART.