LIKE high-tech colleagues of Sherlock Holmes, experts from Lawrence Livermore's Forensic Science Center develop sophisticated analytical equipment for combatting terrorism and the proliferation of weapons of mass destruction, supporting stockpile stewardship efforts, and responding to law-enforcement requests. Using center-developed prototypes, these experts in organic, inorganic, biological, and nuclear chemistry can determine the composition and often the source of the most minute samples of evidence. The sophistication of their sleuthing is beyond the wildest dreams of even Mr. Holmes and Dr. Watson.|
Past issues of this publication have detailed the techniques of the center (E&TR, March 1994, pp. 1-8; and S&TR, August 1995, pp. 24-26). Some of the systems and methods have now "come of age" and are used in the field for remote analyses and real-time results.
This summer in Cape Cod, Massachusetts, the center first used its portable thin-layer chromatography system in the field for the first time. This system interrogated the interior of more than a thousand munitions dating back to World War II. The center also placed modern solid-phase microextraction (SPME) sampling tools at a Department of Energy weapons plant to monitor the safety and efficacy of the current nuclear stockpile. In the law-enforcement arena, the center is a key participant in the new partnership between the Federal Bureau of Investigation (FBI) and Lawrence Livermore (see the box below).
Recipe for Safety: Yellow Cake and Simple Green
In the summer of 1998, Secretary of Energy Bill Richardson announced a new partnership between the Federal Bureau of Investigation (FBI) and Lawrence Livermore to combat international terrorism with high technology. This formal partnership affirms the role the Forensic Science Center plays in supporting forensic investigations.
Two recent incidents--both with happy endings--demonstrate the speed and efficiency with which the center responds to urgent requests from law-enforcement agencies and nuclear regulators.
The first incident involved unknown material in a coffee can obtained by a high school student at a local swap meet. The material--a light yellow, very fine powder--was confiscated by the school. The material was discovered to be radioactive, and the center was called in by DOE.
Nuclear chemist Ken Moody performed the analysis and relayed the results back to DOE within 16 hours of receiving the material. "Since everyone was anxious to get immediate results, we expedited nuclear counting techniques and assayed the material with gamma-ray spectrometry and alpha-particle spectroscopy. We measured no radionuclides above background other than unperturbed isotopes of uranium. The material was naturally occurring uranium, or yellow cake, not an enriched or otherwise processed uranium compound."
The second incident occurred as FBI agents searched the Los Angeles home of a man arrested for stealing military weapons. Among an arsenal of assault rifles, hand guns, explosives, and heavy-duty flak vests, they found a jar of green liquid labeled "poison." Concerned that the liquid might be a chemical warfare agent, the FBI contacted the center.
"Rich Whipple and I conducted field sampling within an FBI-controlled area," explained Pat Grant, deputy director of the center. "We put the sample--which had been well packaged by a hazardous materials team--into a containment glovebag inside a field-portable hood. Using the solid-phase microextraction (SPME) technique, we exposed two microfibers, one at a time, to the liquid and then repackaged the jar. We transported the SPME fibers to the center in O-ring-sealed metal containers. Armando Alcaraz performed gas chromatography-mass spectrometry (GC-MS) analyses, we analyzed and interpreted the data, and the results were reported to the FBI just two-and-a-half hours after the start of our investigation."
Good news. The green substance turned out to be a nontoxic cleaning solution. In fact, the next day Whipple brought in a commercial "simple green" household cleanser and ran a SPME GC-MS analysis of the fluid. The chemical signatures of the commercial product and the suspect solution were virtually identical.
Blast from the Past|
During an environmental cleanup operation at the Massachusetts Military Reservation in the spring of 1998, Army personnel discovered a suspicious depression in an area once used for training. The depression turned out to be the "burial ground" for mortars and ordnance that had been used during target practice exercises (Figure 1, at top). Three questions needed answers: How many of the munitions were "live"? How should they be rendered safe? What was the best way to dispose of them?
Brian Andresen, director of the Laboratory's Forensic Science Center, assessed the situation at the request of the Defense Ammunition Center. His initial samples indicated that approximately one munition out of ten was live, while the rest were dummies of wax and plaster of paris. Although they couldn't explode, the dummies did have live fuses, and some of the rounds--the exact quantity unknown at that point--could have contained appreciable quantities of high explosive (HE).
Andresen recommended cutting each of the thousand--plus mortars in half and sampling them for HE. The Army agreed, so in July 1998 Livermore's Jeff Haas and Greg Klunder packed up sampling kits and analysis equipment and headed east.
The project was an ideal test case for the center's thin-layer chromatography (TLC) screening system, which was originally developed as a field-portable propellant analysis system for the Department of Defense. Propellants (essentially HE) require stabilizers (such as diphenylamine) to prevent spontaneous ignition. Because stabilizers are depleted by extended exposures to high temperatures, the military needed a way to quickly determine the safety of large numbers of bulk propellants. The TLC system screened the Army site for explosive compounds. Sensitive and fast, the system required only 50-milligram samples of explosive, instead of the gram quantities required by other methods, and 15 minutes for each group of 20 samples.
Haas and Klunder analyzed 1,236 mortar rounds in two days (Figure 2). With the real and dummy munitions identified, the Army sent the dummy pieces to a military salvage yard and safely disposed of the remaining live shells. In the past, normal protocol was to group the mortars--live ones and dummies together--in piles of 100 and to explode them all, but that solution is no longer considered environmentally acceptable.
The nearby town of Borne also gained peace of mind from the center's analysis. The work demonstrated that the HE amounts were insignificant and that environmental contamination did not occur while the munitions were buried.
Back to the Future for the Stockpile|
In 1998, center staff also developed methods for verifying the safety of the weapons systems in the U.S. nuclear stockpile.
"Our task was to provide a way of determining the condition of a nuclear weapon's internal components without using either electricity or light and without disturbing the weapon's internal geometry," said Andresen.
The materials in a modern nuclear weapon include highly sensitive and reactive components, such as plutonium and uranium, as well as organic materials. These organic materials include the HE that initiates the nuclear fission reaction as well as structural materials and adhesives that maintain precise internal alignments. Such materials are stable polymers with small diffusion coefficients (10-11 to 10-5 square centimeters per second). However, in the weapon environment--over a period of many years, at elevated temperatures, in a hermetically sealed radioactive environment--certain systems may outgas at detectable levels. When outgassing, these organic materials release compounds that can indicate problems such as corroded metals, degrade components that affect the overall integrity of other warhead materials, and generally signal decomposition of materials within the warhead. By monitoring these chemicals, experts are alerted to problems that may be developing inside the weapon.
The techniques and analytic protocols rely on center-developed solid-phase microextraction (SPME), which allows rapid and efficient environmental sampling and processing. The key to microextraction is a minuscule fiber inside a syringe needle (Figure 3). The fiber is coated with an adsorbant that, when exposed to the ambient environment, collects the molecules of a suitable sample.
Five types of fiber with specialty polymer coatings are available commercially. For example, one fiber picks up acids in preference to bases; another extracts alcohol more efficiently than hydrocarbons. Each SPME fiber coating can collect thousands of different compounds of a specific class after only a few seconds of sampling time. Before the development of this technique, it took weeks to collect and characterize only a few tens of unknown compounds from warhead materials.
In the SPME project, chemists David Chambers and Heather King are identifying the gas-phase chemicals in a weapon's primary headspace and studying their time histories. "In the first phase of this project, we're identifying what chemicals, if any, are emitted by weapon components," said Chambers, the project's principal investigator. "So far, we've characterized weapons-material components as well as HE associated with two weapons systems."|
The most recent stockpile stewardship application of the SPME technique involves monitoring the headspace of individual warheads. For instance, at the Pantex Plant in Amarillo, Texas, SPME is being used with other types of nondestructive surveillance to monitor 10 weapons.
The Future of Forensic Analysis
Key Words: Federal Bureau of Investigation (FBI), Forensic Science Center, gas chromatograph-mass spectrometer (GC-MS), solid-phase microextraction (SPME), thin-layer chromatography (TLC).
For further information contact Brian Andresen (925) 422-0903 (firstname.lastname@example.org).