In the aftermath of suspected chemical attacks, investigators from the Organization for the Prohibition of Chemical Weapons (OPCW) step in to collect chemical, environmental and biomedical samples. Thorough forensic laboratory analysis of these samples is essential for proving what - if any - chemical agents were used and verifying their identities.
Researchers at Lawrence Livermore National Laboratory's (LLNL) Forensic Science Center (FSC) recently developed a new technique to detect pinacolyl alcohol (PA), a unique marker for the nerve agent Soman in environmental samples. The paper has been published in ACS Omega, where it was given the Editor's Choice Award and featured in the journal's cover artwork.
Trusted to safeguard treaty compliance and support high-stakes investigations, LLNL's FSC is one of only two laboratories in the United States certified to receive and analyze real-world samples procured by OPCW sample collection teams. In order to maintain such accreditation, the FSC must successfully complete and pass proficiency tests administered yearly by the organization.
"It is our duty as a Lab not only to provide evidence, if any, for the use of a chemical weapon, but to provide all the analytical evidence to support our findings and in the process support OPCW's efforts in building a case against an alleged perpetrator," said Carlos Valdez, associate program leader for research and development at LLNL's FSC.
As is often the case, nerve agents such as Soman decompose in the environment, leaving low concentrations of potential markers that become difficult to detect. Even with powerful and state-of-the-art instrumentation available at the FSC, a recurring challenge for Valdez and his team is to find trace evidence of a specific marker for a chemical weapon in a sea of more abundant organic and inorganic chemicals present in the matrix.
For Soman, pinacolyl alcohol is a central marker, as it is needed for the synthesis of the nerve agent itself and is also a by-product of its degradation. The alcohol is not a natural chemical but synthetic in origin, making it a unique marker for this highly toxic nerve agent. Therefore, its detection in an environmental sample collected from an area of a suspected chemical attack strongly suggests the past use of the nerve agent.
However, because PA has a low molecular weight, its analysis and correct identification by gas chromatography-mass spectrometry (GC-MS) can be difficult, even at relatively elevated levels. In addition, liquid chromatography-mass spectrometry (LC-MS) analysis is generally not feasible since the chemical does not have ionizable properties.
In their work, the research team at LLNL have developed a method for the conversion of PA into a species that can be effectively detected by both methods, GC-MS and LC-MS, something that currently does not exist in the analytical chemist's toolbox.
"The fact that you can confirm the presence of a specific chemical, in our case PA, by two orthogonal analytical methods is extremely valuable," said Valdez. "It strengthens the official reports to be presented to the OPCW."
The advancement is monumental for proving the presence of Soman and strengthening the evidentiary case in chemical weapons investigations. The next step for the research team is to apply this technique to other alcohols commonly used as markers for various chemical weapons, potentially broadening its impact and utility in forensic analysis.
