Abstract

A review of the literature revealed that investigations into the use of trace metals to determine the geographical origin of heroin have been performed in the past. However, the findings of these studies could not be substantiated due to a lack of seized heroin samples of known provenance with which comparisons could be made. This study involves a novel approach in which opium poppy plants (Papaver somniferum L.) were grown in pots of soil each containing different concentrations of copper, lead and zinc. Leaf and resin samples were collected from each of the plants along with a sample of the soil in which they were grown and, after appropriate sample pre-treatment, the concentrations of copper, lead and zinc were determined using differential pulse anodic stripping voltammetry and atomic absorption spectroscopy. Hierarchical clustering and discriminant function analysis were used to investigate two hypotheses. Firstly, whether resin samples that were known to have originated from plants that were grown in the same soil type could be clustered together and secondly, whether resin samples could be linked back to the soil from which the corresponding poppy plants were grown. The findings showed that when soil types with a greater difference in concentrations of copper, lead and zinc were considered, metal concentration ratios in resin could be used to determine the soil in which the corresponding poppy plants had been grown. However, the classification techniques proved to be more successful when attempting to cluster together resin samples that were known to have originated from poppy plants that were grown in the same soil type. iii In comparison to the findings of this study, previous studies demonstrated a greater ability to distinguish between seized heroin samples of different origins using the same classification techniques. This suggests that the addition of metals from sources other than the soil contributed towards making the samples of heroin unique.