What You See Is What You Get
By combining three technologies into a single system--an ion trap mass spectrometer for analysis, a high-powered microscope for viewing, and a laser for ionizing samples--the Center has created something entirely new for forensic analysis: imaging laser-ablation mass spectroscopy. Conceived in 1994 and still being refined, this new process allows considerably more accuracy in analyzing samples than standard mass spectroscopy.
Sampling material is placed on the tip of a probe that is inserted into the source region of an ion trap mass spectrometer. With a microscope outside the vacuum chamber, the sampling material is viewed from above at 250 ¥ magnification. A laser beam is then directed at precisely the 10- to 50-micrometer spot on the probe tip from which the sample's mass spectral data is desired. The intensity of the laser beam can be adjusted to instantaneously vaporize more or less sampling material, depending on the size of the sample. The laser ionizes the material, and the mass spectrometer sorts these fragments according to their molecular weights. Once sorted, each chemical component produces a characteristic mass spectral fragmentation pattern that is used by the operator to identify the entire sample.
There are several benefits of this method. The new imaging capability allows for a more accurate focus of the laser beam, which means more accuracy in sampling and more accuracy in analysis. By having the sampling material inside the mass spectrometer vacuum chamber before it is hit with the laser beam, sample losses are far less than when the sample is bombarded outside the ion source and then transferred to the mass spectrometer. We can also analyze smaller particles and fibers with this system than we can with a standard bench-top ion trap.
This new system has numerous applications. One possible use is to provide a chronological record of chemical exposures by analyzing hair, vegetation, and other materials. For example, ingestion of or exposure to certain chemicals, including illegal drugs, can be identified in human hair. Since human hair generally grows at about one-half inch per month, analysis of a person's hair along its length can provide a chronology of drug use over time (see photos above). Or the hair of a dog known to have been kept as a pet at a suspected drug manufacturing facility can be analyzed to determine chemicals associated with chemical spills and exposures at the drug lab. Positive identification of chemicals in the dog's hair, indicative of the lab's operations, could serve as criminal evidence in a trial.
Although this technique is still in its infancy, its potential could be enormous. As lasers become easier to use, smaller and smaller particles and fibers will be sampled and characterized in forensic investigations.

Miniaturizing the GC/MS
The Forensic Science Center is also at the forefront in developing new, portable systems capable of real-time analysis in the field. These units have numerous applications, from identifying materials to support verification of the Chemical Weapons Convention to investigating criminal activities.
Almost five years ago, the Center developed a suitcase-size gas chromatograph/mass spectrometer (GC/MS) for on-site identification of ultratrace (microgram or less) quantities of certain compounds in complex mixtures. The system weighed 68 kg (150 lb), which made it portable, but only barely. Three years later, the system's weight had been cut by more than half to 32 kg (70 lb), still a hefty load. Today, at 20 kg (44 lb), with an accompanying laptop computer, this system can realistically be considered portable. This rugged, all-metal vacuum vessel can be carried on board an airplane and put into the overhead compartment, while its accompanying generator and off-line vacuum reconditioning pumping unit travel in the baggage compartment.

Counter-Forensic Inspection
In the summer of 1994, DOE asked the Forensic Science Center to perform a preliminary "counter-forensic" analysis to help the government investigate vulnerabilities of two gaseous-diffusion, uranium-enrichment plants that will be subject to international inspections. Although inspections of the plants are expected to be visual only, DOE wanted to know whether a hypothetical inspector with a different agenda, while walking through one of its plants, could surreptitiously collect samples of material, take them home, examine them, and replicate the enrichment process. The Center's mission was to examine the similar samples and learn critical details of the enrichment process.
In the gaseous diffusion enrichment process, uranium hexafluoride passes through a series of semipermeable barriers, the number of barriers being determined by the enrichment required. Uranium used in power reactors requires less enrichment than weapons-grade uranium, which is highly enriched.
The Center used for its analysis a variety of materials collected from different areas in the plant. With minute quantities of these materials and state-of-the-art analytical equipment, our chemists, engineers, and metallurgists were able to determine whether or not various aspects of the enrichment process are vulnerable to surreptitious collections. We expect these results to be useful in determining future inspection protocols.