EA-IRMS: Tracing the geographical origin of cocaine

Importance of the Topic

Cocaine is a globally prevalent illicit drug, and understanding its geographic origin is critical for law enforcement to identify cultivation areas and trafficking routes. Bulk stable isotope analysis offers a reliable means to link seized cocaine back to its source by reflecting environmental signatures preserved during production.

Objectives and Study Overview

This study aimed to evaluate whether isotope fingerprints of carbon (δ13C), nitrogen (δ15N), hydrogen (δ2H) and oxygen (δ18O) in coca leaves and seized cocaine can be used to delineate production regions at both regional and sub-regional scales across South America.

Methodology and Instrumentation

• Sample Collection: 572 coca leaf samples were obtained from 19 known growing regions in Bolivia, Colombia and Peru to build a reference database.
• Isotope Analysis:
  • Carbon and nitrogen isotopes (δ13C, δ15N) were measured by EA-IRMS after combustion in an elemental analyzer with internal atropine and benzoic acid standards calibrated to VPDB and AIR.
  • Hydrogen and oxygen isotopes (δ2H, δ18O) were measured by pyrolysis at 1400 °C, with internal C-28, C-34 and atropine secondary standards calibrated to VSMOW and AIR.

Used Instrumentation

• Thermo Scientific EA-IRMS System with combustion/reduction reactors for δ13C and δ15N.
• Pyrolysis reactor-equipped EA-IRMS for δ2H and δ18O analyses.

Main Results and Discussion

• Isoscapes constructed for each isotope revealed distinct spatial patterns correlating with altitude, rainfall, and local environmental conditions.
• Combining isotope fingerprints with trace alkaloid profiles and multivariate statistical analysis improved the classification of seized cocaine to specific South American growing regions, including differentiation within Colombia.
• Case Study: Analysis of an "aircraft drop" in Uruguay led to identification of a previously unrecognized coca cultivation area in Beni, Bolivia, demonstrating the method’s ability to discover new production zones.

Benefits and Practical Applications

• Provides law enforcement agencies with robust forensic evidence to trace cocaine seizures back to cultivation sites.
• Enhances intelligence by pinpointing emerging or unknown coca growing regions.
• Supports strategic decision-making in counter-narcotics operations.

Future Trends and Potential Applications

• Expansion of isotopic and alkaloid databases for broader geographic coverage and higher resolution mapping.
• Integration with additional isotopic systems (e.g., sulfur, strontium) to further refine origin assignments.
• Application of real-time or portable IRMS technologies for in-field screening.
• Advancements in chemometric and machine learning approaches to enhance classification accuracy.

Conclusion

Stable isotope fingerprinting of cocaine complements traditional profiling techniques and offers a powerful tool for tracing the geographic origin of illicit drugs. By reflecting environmental conditions of cultivation, this approach supports law enforcement in identifying and disrupting trafficking networks.

References

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