ISOTOPIC AND ELEMENTAL ANALYSIS FOR THE FORENSICS AND ATTRIBUTION OF BIOLOGICAL AGENTS

In the event of a biological weapon attack, the agent and strain are initially identified by biological analyses. However those genetic data yield limited attribution information, because many pathogens are genetically very homogeneous. There is a need for more informative forensic analyses for the attribution of the agent to a source and its production method. Chemical compositions such as those provided by elemental and isotopic analyses may provide further insight into production processes and growth media used. Ideally, one may be able to compare known and questioned biological weapon agents to determine the degree of association based on isotopic and elemental contents. Modeling with advanced statistical analyses and extended database could narrow down possible production sources and methods.

In support of the U.S. Department of Homeland Security, a series of investigations have been performed to develop and validate methods for high precision isotope ratio and elemental composition analysis. One goal is to identify signatures related to biological weapon agent processing techniques and materials by means of the isotopic and elemental analysis of several bacterial agents that were grown under controlled conditions. Results on method development and analytical characterization will be presented of both “light” (e.g, C, N, O, and H by means of elemental analyzer/gas chromatograph isotope ratio mass spectrometry) and “heavy” isotope ratio measurements (e.g. Sr, Pb by multiple-collector ICP mass spectrometry and multiple-collector thermal ionization mass spectrometry). Effects of growth media and processing on elemental and isotopic profiles will be highlighted. The utility of statistical analysis and the importance of database development are also discussed.

Research sponsored by the Office of Research and Development, U.S. Department of Homeland Security, under contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC. HKM gratefully acknowledges support from the US Central Intelligence Agency, and ML support from the Fulbright Foundation.