Analyzing cannabis flowers according to the German Pharmacopeia - monograph 2017

Importance of the Topic

The 2017 legal amendment in Germany increased the need for robust analytical methods to ensure the quality and accurate labeling of medicinal cannabis products. High-performance liquid chromatography (HPLC) methods aligned with the German Pharmacopoeia monograph provide reliable quantification of key cannabinoids critical for patient safety and regulatory compliance.

Objectives and Study Overview

This study aimed to develop and verify an HPLC method for simultaneous quantification of six major cannabinoids (CBD, CBDA, CBN, Δ8-THC, Δ9-THC, Δ9-THCA) in cannabis flowers. The approach included a robustness evaluation across three reversed-phase columns and verification using market-available medicinal cannabis samples.

Methodology and Instrumentation

A design of experiments (DoE) approach utilizing DryLab software screened gradient time, column temperature, mobile phase pH, and stationary phase type to identify robust operating conditions. Sample preparation involved grinding 5 g of cannabis flower, triple extraction of 500 mg with ethanol, centrifugation, and a 1:10 dilution. Analysis was performed on an AZURA HPLC plus system comprising an LPG pump, MWD detector at 225 nm and 306 nm, autosampler, and column thermostat. Three Eurospher II columns (C18, C18H, C18P) were evaluated at 40°C with a water–acetonitrile gradient (35–65% organic to 20–80% over 37 minutes) at 1.0 mL/min.

Main Results and Discussion

Column C18P demonstrated the largest robust design space with critical resolution (>1.6) maintained over the tested pH and temperature ranges. Standard mixture chromatograms achieved a resolution of 1.5 between Δ8-THC and Δ9-THC, exceeding the monograph requirement of R>1.2. Analysis of a Bedrocan sample confirmed peak assignments; unidentified signals likely represent matrix interferences or minor cannabinoids. Dual-wavelength detection effectively differentiated acidic and neutral cannabinoid forms.

Benefits and Practical Applications

• Provides a validated pharmacopoeia-compliant HPLC method for routine quality control laboratories
• Ensures reliable separation and quantification of key cannabinoids for GMP-regulated production
• Supports accurate product labeling and consumer safety

Future Trends and Opportunities

• Integration of ultra-high-performance liquid chromatography for faster analysis
• Coupling with mass spectrometry to expand cannabinoid profiling and detect trace components
• Automation and high-throughput workflows to accommodate growing analytical demand
• Application of chemometric tools for further method optimization and multivariate data analysis

Conclusion

A DoE-driven column screening with DryLab software efficiently identified robust HPLC conditions. The validated method achieved pharmacopoeial separation criteria and successfully quantified six major cannabinoids in real samples, offering a dependable tool for medicinal cannabis quality control.

References

1. German Narcotics Law (Betäubungsmittelgesetz, BtMG) as amended March 2017
2. German Pharmacopoeia 2017, Deutsches Arzneibuch Monograph DAB
3. Hoch E, Friemel CM, Schneider M. Cannabis Eine Wissenschaftliche Bestandsaufnahme Springer 2018
4. Grotenhermen F. Endogene Cannabinoide und das Endocannabinoidsystem In Handbuch Psychoaktive Substanzen Springer 2018 pp 411-420
5. Guideline on Good Agricultural and Collection Practice GACP for starting Materials of Herbal Origin EMEA/HMPFC/2468167/2006
6. Smith BC Inter-Lab Variation in the Cannabis Industry Part I Problem and Causes Cannabis Science and Technology 2019 Vol 2 No 2