Quality control of dried cannabis

Importance of the Topic

Determining the cannabinoid profile of dried cannabis is critical for regulatory compliance, medical dosing, and product quality assurance.
The main bioactive compounds (THC, CBD, CBG) exert distinct effects, with different legal statuses across jurisdictions.
The growing cannabis industry demands fast, reliable, and reagent-free analytical methods suitable for both lab and production environments.

Objectives and Study Overview

The study aimed to develop and validate a near-infrared spectroscopy (NIRS) approach to quantify THC, CBD, and CBG in dried cannabis within one minute.
A total of 702 samples with varying cannabinoid contents were analyzed to build robust calibration models and compare NIRS predictions against the reference HPLC method.

Methodology

Samples (400 mg each) were ground manually and placed in disposable mini reflectance cups.
Vis–NIR spectra (400–2500 nm) were collected with a DS2500 Solid Analyzer using a 4 mm gold diffuse reflector in transflection mode.
Multivariate calibration models were developed and validated using the Vision Air Complete software, employing cross-validation to assess prediction performance.

Instrumentation Used

• Metrohm DS2500 Solid Analyzer (400–2500 nm)
• DS2500 Holder and mini sample cups with disposable backs
• 4 mm gold diffuse reflector for transflection measurements
• Vision Air 2.0 Complete software for data acquisition and model development

Main Results and Discussion

High correlation between NIRS predictions and HPLC reference values demonstrated the method’s accuracy.

• THC: R2=0.979; calibration error 0.71 %, cross-validation error 0.73 %
• CBD: R2=0.978; calibration error 0.74 %, cross-validation error 0.75 %
• CBG: R2=0.849; calibration error 0.16 %, cross-validation error 0.17 %

The slightly lower correlation for CBG reflects its lower concentration range and higher variability among samples.
The NIRS models provided consistent performance across diverse sample matrices, indicating robust predictive capability.

Benefits and Practical Applications of the Method

The NIRS approach offers key advantages over conventional HPLC:

• Rapid analysis in under one minute versus approximately 30 minutes total for HPLC (including preparation)
• Chemical-free and non-destructive testing
• High sample throughput with minimal user training
• Portable and robust instrumentation suitable for production environments

Future Trends and Applications

Advancements in portable NIR instruments and cloud-based calibrations will enable on-site potency testing at cultivation facilities and dispensaries.
Expanding spectral libraries can facilitate simultaneous quantification of additional cannabinoids and terpenes.
Integration of NIRS with process analytical technology (PAT) could support real-time process control during extraction and formulation.

Conclusion

The validated NIRS method reliably quantifies THC, CBD, and CBG in dried cannabis, delivering accurate, reproducible results in under one minute without chemicals.
This rapid, non-destructive technique addresses key challenges in cannabis quality control and supports regulatory and industrial testing needs.