Trace isotope analysis of Ricinus communis seed core for provenance determination by laser ablation-ICP-MS

The castor bean plant, Ricinus communis, grows wild throughout many regions of Australia. The seeds of the plant contain the schedule 1 chemical agent ricin, a type II ribosomal inhibiting protein. Currently there are limited analytical techniques that can be applied in analysis of the seeds to establish attribution. In this study, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used for the analysis of seeds collected from 68 plants across 38 locations around Australia. Of the 92 elemental isotopes measured, fifteen (24Mg, 27Al, 44Ca, 53Cr, 55Mn, 57Fe, 60Ni, 65Cu, 66Zn, 75As, 85Rb, 88Sr, 98Mo, 138Ba and 202Hg) yielded data that were relevant to all collection sites. Data were further analysed using multivariate statistical analysis which facilitated the potential for the identification of unique provenance isotopes. Furthermore, this analysis indicated that 59Co was present at significant levels in Victorian and Sydney specimens only.