Determination of Moisture in Cannabis

Significance of the Topic

Moisture content is a critical quality attribute in cannabis production and processing. It influences microbial stability, shelf life, and extraction efficiency for cannabidiol (CBD) and other compounds. Accurate moisture determination helps prevent mold growth, standardize dry-basis calculations of active constituents, and ensures compliance with emerging regulatory requirements.

Objectives and Study Overview

This application note presents a thermogravimetric analysis (TGA) method using the LECO TGM800 to quantify moisture in both cured and uncured cannabis samples. The study aims to demonstrate the method’s precision, accuracy, and throughput capacity for routine quality control in cannabis production.

Applied Methodology and Instrumentation

The TGA approach measures mass loss on drying under controlled temperature and atmosphere. Key elements include:

• Instrument: LECO TGM800 thermogravimetric analyzer with four-place balance and multi-sample oven (up to 16 positions)
• Atmosphere: Nitrogen flow at 4.0 L/min
• Temperature program: Ramp from 25 °C to 80 °C at 20 °C/min, hold for 30 min, end at mass constancy (0.0005 g over a 9 min window)
• Sample mass: Approximately 1.0 g per analysis, using small (1.5 in) or large (2.4 in) aluminum foil crucibles
• Sample preparation: Ground cured samples with a hand tobacco grinder; fresh/uncured samples with a knife mill; seed removal to enhance reproducibility

Main Results and Discussion

Results for moisture content showed:

• Cured recreational cannabis: average 8.07 % (s = 0.22)
• Cured hemp cannabis batch #1: average 7.30 % (s = 0.14)
• Cured hemp cannabis batch #2: average 7.41 % (s = 0.24)
• Fresh hemp cannabis batch #1: average 73.99 % (s = 0.19)
• Fresh hemp cannabis batch #2: average 73.94 % (s = 0.22)

Low standard deviations confirm high method precision. The selected 80 °C drying temperature minimizes loss of volatile organics compared to the USP-recommended 105 °C.

Benefits and Practical Applications

The TGM800 TGA method offers:

• Simultaneous analysis of up to 16 samples for high throughput
• Automated data processing for moisture calculation based on mass ratio
• Robust performance suitable for process control in drying, curing, and oil extraction workflows
• Enhanced reproducibility through standardized sample preparation and instrument parameters

Future Trends and Potential Uses

Emerging directions include integration of chemometric modeling for moisture prediction, coupling TGA with evolved gas analysis to profile terpenes and residual solvents, and fully automated sample handling to further increase laboratory efficiency. Expansion of regulatory guidelines will drive broader adoption of TGA-based moisture testing across cannabis quality assurance programs.

Conclusion

The LECO TGM800 thermogravimetric method provides a precise, accurate, and efficient solution for moisture determination in cannabis. Its ability to handle multiple samples concurrently and deliver consistent results supports critical quality control steps in cultivation, curing, and extraction processes.

Reference

1. USP Monograph 731: Loss on Drying Method (modified for 80 °C drying)
2. USP Monograph 921: Water Determination Method (modified for TGA)
3. LECO Pittcon Poster “Determination of Moisture/Loss on Drying in Cannabis by Various Analytical Techniques”