Nuclear techniques in forensic toxicology

Abstract

Illegal trades carried out by criminal organisations are a major threat to health and security worldwide. Criminal organisations are trading both drugs of abuse and illegal pharmaceutical products and supplements. The aim of our research is to show how nuclear techniques can support the protection of public health and the fight against illegal trades of interest for forensic toxicology, providing key analytical information. Specimens of Cannabis sativa L. were analysed by instrumental neutron activation analysis for Al, As, Br, Ca, Cd, Co, Cs, Fe, K, La, Mg, Mn, Na, Rb, Sb, Sc, Sm, Sr, V, and Zn. Illegal pharmaceutical products containing sildenafil and preparations containing oxandrolone (a doping agent) were analysed by accelerator-based nuclear analytical techniques, such as Ion Beam Analysis (IBA), for elemental analysis, and by Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) and Gas Chromatography coupled to mass spectrometry (GC-MS) for organic analysis. IBA analysis by PIXE (Particle-Induced X-ray Emission), PIGE (Particle-Induced Gamma-ray Emission) and EBS (Elastic Backscattering Spectrometry) were carried out using an accelerated proton beam extracted in air with no sample preparation. Statistical evaluation was carried out by hierarchical cluster analysis and principal component analysis. Several elements (F, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Br and Sr) were identified in the illegal products containing sildenafil (6 specimens) or oxandrolone (6 specimens) by PIXE, allowing their quantitative elemental characterisation. Secondary ion mass spectrometry using primary ions with energies in the range of several MeV (MeV-SIMS) provided analysis of organic active compounds and organic impurities. The traditional approach based on chromatography coupled to mass spectrometry provided complementary organic analysis. Authentic Viagra was also analysed. Cluster analysis of the results from 63 specimens was able to group the Cannabis specimens into their known or reported growing regions with a high degree of accuracy. Principal component analysis was also able to elucidate some of the underlying geochemical factors that could explain the clustering. The IBA results showed that a simple criterion suggested in a previous work to identify authentic Viagra is valid also for the analysis carried out in different laboratories (LABEC accelerator of the INFN Division of Florence and IIL in Brazil). Nuclear techniques showed to be effective to support the protection of public health and the fight against illegal trades of interest for forensic toxicology, providing key analytical information inaccessible with traditional analysis by LC-HRMS and GC-MS). Timely analytical results are needed to provide early warning for public health. Nuclear techniques should be further studied to allow a global inter-laboratory classification system of drugs of abuse, doping products and illegal pharmaceutical products. The elemental characterisations provided is complementary to the organic information obtained by the traditional analytical approach based on chromatography coupled to mass spectrometry. Global databases could allow inferring about common characteristics of illegal products such as provenience of bulk materials, site of production etc., providing key forensic information to support the fight against illegal trades.