Tracing the geographical origin of cocaine

Cocaine carries a chemical fingerprint from the region where the coca was grown. Here we show that cocaine originating from different geographic regions in South America can be identified by its isotope-ratio signature. The distinct carbon (δ 13 C) and nitrogen (δ 15 N) isotope-ratio combinations allow the country of origin to be determined for the principal coca-growing regions along the Andean Ridge. By combining this information with detectable differences in the patterns of the trace alkaloids truxilline and trimethoxycocaine, we correctly identified the source of 96% of 200 cocaine samples.