CBD purification – Part 2: Transfer and optimization of a purification method in preparative scale

Significance of Topic

The purification of natural products like cannabidiol (CBD) is vital for pharmaceutical, nutraceutical and research applications. Preparative liquid chromatography offers lower energy and water consumption compared to traditional methods while delivering high yields and purity from complex plant matrices.

Aims and Overview of Study

This article presents the transfer and optimization of a preparative HPLC batch process to isolate CBD from a CBD-rich cannabis extract. Key objectives included establishing a robust method, maximizing CBD recovery and purity, and evaluating the loading capacity of the preparative column.

Methods and Instrumentation

The method employed a preparative HPLC system with a 250 ml/min pump and a ternary LPG module using an ethanol–water gradient. The CBD-rich ethanol extract was filtered prior to injection. Overload studies were conducted by increasing injection volumes to monitor peak shape and fronting. Fraction collection windows were defined based on chromatographic behaviour to balance purity and yield.

Main Results and Discussion

Peak distortion occurred at injection volumes above 4 ml. A 4 ml injection provided reproducible CBD separation with minimal broadening. Fraction analysis identified CBD-rich fractions with up to 99.8 % purity. Pooling fractions eluting between 5.5 min and 9.5 min (fractions 7–13) yielded 137 mg CBD with 97 % purity and 95 % recovery from 4 ml of extract.

Benefits and Practical Applications

The optimized method delivers high-purity CBD suitable for pharmaceutical and research use while reducing solvent and energy requirements. Its adaptability makes it applicable to the purification of other valuable compounds from complex natural mixtures.

Future Trends and Possibilities of Use

Future developments may include continuous chromatography for higher throughput, automated fraction handling for seamless scale-up, and the adoption of greener solvents to further reduce environmental impact.

Conclusion

A robust preparative HPLC protocol for CBD purification was successfully developed and optimized. The method demonstrated high reproducibility, achieving 95 % recovery and 97 % purity, confirming batch preparative chromatography as an effective tool for natural product isolation.

Used Instrumentation

• Preparative HPLC system with 250 ml/min pump and ternary LPG module
• Semi-preparative UV detector (228 nm) with flow cell
• Fraction collector with 8-port injection valve and sample pump
• Eurospher II C18 preparative column (250 × 20 mm, 15 µm)
• Dynamic mixer, eluent tray and assistant module

Reference

• Blanc CL et al. Separation and Purification Technology 2015.
• Pertwee RG. Handbook of Cannabis, OUP 2014.
• Aizpurua-Olaizola O et al. Journal of Natural Products 2016.
• Turner CE et al. Journal of Natural Products 1980.
• Hazekamp A. Medical Cannabis and Cannabinoids 2018.
• Perez E et al. Molecules 2022.
• ElSohly MA. Marijuana and the Cannabinoids 2007.
• Loxterkamp L, Monks K. KNAUER application note 2020.