Stability of cocaine impurity profiles during 12 months of storage.

During the lifetime of a cocaine batch from production end to consumption, several alterations may occur, leading to possible changes in the original impurity profile. Such profile changes may eventually result in erroneous forensic evaluations. In the present study, the stability of both the alkaloid and the residual solvent impurity profiles of cocaine were evaluated over a period of 12 months under different storage conditions (temperature, purity and weight) using GC-MS and HS-GC-MS, respectively. The sample purity (p<0.001), time of storage (p<0.001) and storage temperature at 37°C (p<0.01) significantly influenced the alkaloid impurity profile. The most significant change was observed in low purity samples stored at 37°C. In contrast, no changes were observed in the residual solvent profile at all storage conditions for the entire 12-month study period. This finding indicates that the residual solvent profile may be more applicable than the corresponding alkaloid profile when cocaine seizures subjected to different storage conditions are compared. Our results clearly demonstrate that cocaine alkaloid profiles change over time and are most susceptible to sample purity and storage temperature. As a consequence, storage conditions and purity should be taken into account when cocaine comparison is conducted in criminal cases.