Application of carbon and nitrogen stable isotope and elemental composition data for Ricinus communis sample comparison and correlation

Abstract

Recent years have highlighted the global threat posed by biotoxins. Particularly the plant toxin ricin, found in the seeds of the castor oil plant Ricinus communis, is of special forensic interest due to its worldwide availability, high toxicity, and lack of medical countermeasures. We investigated the combination of carbon and nitrogen stable isotope measurements with respective elemental composition data to provide additional forensic intelligence for sample comparison and correlation. For this, we purchased seeds from three commercially available cultivars of Ricinus communis and lipid-extracted these with three different protocols. By considering C and N stable isotope data alone, 97% of samples were correctly classified in pairwise comparison. The model was further enhanced by including total carbon and nitrogen content data, which provided information about the level of extraction and allowed the development of a normalization model based on carbon isotope ratios and carbon content. Such a model can be used not only to compare unknown samples, but also to estimate the carbon isotope ratios of original seeds and correlate potential source seeds found at a preparation site to seized extracted materials. Unlike previous approaches, this model is independent of the specific extraction method, as it reflects the systematic carbon isotope shifts across different extraction levels rather than method-specific fractionation effects. Thus, isotope ratio mass spectrometry (IRMS)-based profiling of Ricinus communis materials can help to retrospectively categorize and correlate ricin-containing materials. This information can be implemented in profiling strategies and is of high value for forensic intelligence in the context of sample comparison.