Forensic Applications of Light-Element Stable Isotope Ratios of Ricinus communis Seeds and Ricin Preparations

Authors

  • Helen W. Kreuzer Ph.D.,

    Corresponding authorCurrent affiliation:
    1. Chemical and Biological Signature Sciences, Pacific Northwest National Laboratory, 999 Battelle Blvd, MSIN P7-50, Richland, WA 99352
    • Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112
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  • Jason B. West Ph.D.,

    1. Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112
    Current affiliation:
    1. Department of Ecosystem Science and Management, , Horticulture/Forest Science Building, Room 305, College Station, TX 77843
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  • James R. Ehleringer Ph.D.

    1. Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112
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  • This work was funded by the Federal Bureau of Investigation, BAA Solicitation Number: BAA-0034104, Interest Area 103. H.W.K. also received support from the Laboratory Directed Research and Development Program at Pacific Northwest National Laboratory, a multiprogram laboratory operated by Battelle for the U.S. Department of Energy under Contract DE-AC05-76RL01830. Funding from the National Science Foundation (Grant no. 0743543) to J.B.W. provided partial support for this work.

Additional information and reprint requests:

Helen Kreuzer, Ph.D.

Chemical and Biological Signature Sciences

Pacific Northwest National Laboratory

999 Battelle Blvd, MSIN P7-50

Richland, WA 99352

E-mail: Helen.Kreuzer@pnnl.gov

Abstract

Seeds of the castor plant Ricinus communis are of forensic interest because they are the source of the poison ricin. We tested whether stable isotope ratios of castor seeds and ricin preparations can be used as a forensic signature. We collected over 300 castor seed samples worldwide and measured the C, N, O, and H isotope ratios of the whole seeds and oil. We prepared ricin by three different procedures, acetone extraction, salt precipitation, and affinity chromatography, and compared their isotope ratios to those of the source seeds. The N isotope ratios of the ricin samples and source seeds were virtually identical. Therefore, N isotope ratios can be used to correlate ricin prepared by any of these methods to source seeds. Further, stable isotope ratios distinguished >99% of crude and purified ricin protein samples in pairwise comparison tests. Stable isotope ratios therefore constitute a valuable forensic signature for ricin preparations.

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