Fast, Easy, and Reliable Monitoring of THCA and CBDA Decarboxylation in Cannabis Flower and Oil Samples Using Infrared Spectroscopy

Importance of the topic

Cannabinoid decarboxylation is a critical post‐processing step in cannabis and hemp production that converts naturally occurring acidic forms (THCA and CBDA) into their neutral, psychoactive counterparts (THC and CBD).
Cultivators and extractors must balance complete conversion against overprocessing, which can degrade target compounds, increase costs, and reduce product quality.

Objectives and Study Overview

This work aimed to develop a fast, user-friendly, near-real-time monitoring method for THCA and CBDA decarboxylation in both flower and oil matrices.
The goal was to fill gaps in standard process control by leveraging infrared spectroscopy to track reaction progress without lengthy chromatographic analysis.

Methodology and Instrumentation

Sample preparation and analytical workflow were designed for ease of use on the production floor:

• Flower samples: ~200 mg milled material extracted with pentane and sonicated for 2 minutes, then solvent allowed to evaporate on an ATR crystal.
• Oil samples: neat extract directly applied to the ATR crystal.
• IR data acquisition: Agilent Cary 630 FTIR spectrometer with diamond ATR (ZnSe) optics, controlled via Agilent MicroLab software.
• Reference analysis: Agilent 1220 Infinity II HPLC system to quantify THCA/THC and CBDA/CBD for model calibration.

PCA‐based calibration models were built and validated by correlating IR spectral changes to % decarboxylation determined by HPLC across temperature (75–150 °C) and time (25–90 min) ranges.

Main Results and Discussion

The IR prediction models demonstrated strong agreement with HPLC reference data:

• THCA→THC in oil: R² = 0.961.
• CBDA→CBD in oil: R² = 0.987.
• THCA→THC in flower: R² = 0.953.

Model accuracy was highest during the final 5–10 minutes of reaction, enabling precise endpoint detection. The MicroLab software presents color-coded, actionable results within seconds, guiding operators to continue or terminate heating.

Benefits and Practical Applications

The IR‐based monitoring approach offers:

• Rapid feedback (<1 minute per measurement) versus ~1 hour for HPLC.
• Minimal sample consumption (≈200 mg flower or few μL oil).
• No specialized analytical training or large laboratory footprint required.
• Improved process control to avoid under- or over-decarboxylation, preserving yield and product quality.

Instrumentation

• Agilent Cary 630 FTIR spectrometer with diamond ATR (ZnSe) module.
• Agilent MicroLab software with built-in decarboxylation workflow and PCA model.
• Agilent 1220 Infinity II HPLC system for reference analyses.

Future Trends and Potential Applications

Opportunities for further development include:

• Extending IR models to additional minor cannabinoids and terpene profiles.
• Integrating real-time spectral monitoring into automated decarboxylation reactors.
• Applying machine learning to predict optimal parameters for diverse biomass batches.
• Combining IR data with other spectroscopic techniques for comprehensive quality control.

Conclusion

The Agilent Cary 630 FTIR platform coupled with a PCA‐based decarboxylation model delivers a reliable, rapid, and user-friendly solution for monitoring THCA and CBDA conversion in cannabis flower and oil. This approach empowers producers to optimize reaction endpoints, enhance product consistency, and reduce processing costs.