MRICD chemists develop kit to simplify chemical agent exposure verification

Prototype Forensic Liquid Analysis Kit developed by the U.S. Army Medical Research Institute of Chemical Defense. | U.S. Army photo by Darrell Jesonis

ABERDEEN PROVING GROUND, Md. — The Analytical Chemistry Team at the U.S. Army Medical Research Institute of Chemical Defense, known as MRICD, has developed a compact, low cost, and efficient Forensic Liquid Analysis Kit, or FLAK, to facilitate the verification of exposure to chemical warfare agents by overcoming the logistical burden of transporting a liquid sample to a reference laboratory for analysis.

The kit can be used to test urine samples to verify human exposure and environmental water samples to verify contamination with the chemical agents.

According to Dr. Brian Pate, the project’s manager in the Defense Threat Reduction Agency’s Chemical and Biological Technologies Department, “Once deployed, the kit will enable prompt and reliable sampling for greatly improved verification of field exposures to chemical warfare agents, allowing warfighters to react quicker and more appropriately for the threats in the area.”

Artist rendering of the FLAK sampling process. | U.S. Army illustration

Exposure in an individual is verified by collecting a urine sample and then analyzing the sample for the breakdown products, called analytes, that result from the body’s metabolism of the chemical warfare agent. Detection of these analytes confirms the exposure occurred and identifies the specific chemical warfare agent involved.

The MRICD is one of the reference laboratories that receives and analyzes urine samples from suspected exposure events, and these samples need to be frozen during transit. Furthermore, urine samples from OCONUS are occasionally delayed in Customs over safety concerns, even though the samples themselves do not contain chemical warfare agents and are not hazardous.

Led by Dr. Benedict Capacio, the Analytical Chemistry Team began looking for ways to overcome these obstacles and found it in the technology of solid phase microextraction fibers, which are being used commercially for the collection of a variety of samples, to include water and air.

Sorting through the different types of fibers on the market, the team chose one that could not only work with the compounds to be sampled but also be used with liquid chromatography, an analysis technique that, at the time, was not compatible with many of the available fibers. The team then made adjustments to the process for sampling and desorption from the fibers to optimize the detection of chemical warfare agent analytes. These adjustments included determining the best sample volume, pH, and length of time the fibers needed to be in the sample for analyte adsorption onto the fibers, as well as the optimal solvent, solvent volume, and fiber time in solvent to maximize analyte desorption from the fibers.

With funding from the Defense Threat Reduction Agency, the team partnered with a private business to create a prototype. The FLAK contains two small bottles, one with an internal standard and one with hydrochloric acid, both of which are added to the sample to facilitate the subsequent analysis process. The fibers are encased in a metal shaft from which they are released into the sample for adsorption and then retracted. Once the sample is acquired the fiber syringe is placed in a Falcon tube, which goes into a shipping cylinder with a label for shipment to the reference laboratory. Upon arrival at the laboratory, the sample is removed by inserting the fibers into an organic solution, which is then analyzed with standard liquid chromatography-mass spectrometry techniques.

After confirming the kit’s accuracy, the team performed rigorous tests to ensure that the entire kit and sample-adsorbed fibers would stand up to various environmental stress conditions. Conditions tested included extreme hot and cold temperatures, sudden changes in temperature extremes, and high humidity levels. Additionally, they tested the stability of the analytes on the fiber in a two-year study. The FLAK passed these tests with flying colors.

While the FLAK was intended for use by forward field units to confirm exposure to chemical warfare agents, it could also be useful to test for exposure of noncombatant casualties.

Pate points out, “as demonstrated by recent events in Syria, prompt and definitive verification of chemical agent exposure can dramatically impact international response to suspected use of chemical warfare agents by terrorists or rogue nations.”

MRICD’s chemists are now working on a second generation kit that will detect exposure to organophosphorus pesticides, hazardous chemicals that are similarly toxic to chemical warfare agents but far more common. Based on exposures reported to the U.S. Environmental Protection Agency, at least 20,000 agricultural workers are estimated to be poisoned by pesticides each year.

By Cindy Kronman, Medical Research Institute of Chemical Defense