Cannabis Analysis: Potency Testing Identification and Quantification of THC and CBD by GC/FID and GC/MS

Importance of the Topic

Analysis of cannabis potency has become critical following legalization in multiple jurisdictions. Accurate measurement of psychoactive THC and therapeutic CBD levels supports regulatory compliance, market valuation and medical dosing. The THC/CBD ratio informs growers, dispensaries, clinical practitioners and tax authorities about product quality, efficacy and safety.

Objectives and Study Overview

This study outlines gas chromatographic methods for identification and quantification of THC and CBD in botanical and extract samples. It compares GC/FID and GC/MS approaches, addresses sample preparation and explores method suitability for recreational and medicinal cannabis products. HPLC approaches for cannabinoid acid detection are discussed as complementary techniques.

Methodology and Instrumentation

Sample Preparation

• 50–100 mg dried plant material ground to pass a 1 mm mesh
• Extraction with methanol or equivalent solvent, sonication and filtration
• Optional decarboxylation at elevated temperature to convert THCA and CBDA to THC and CBD

Gas Chromatography Conditions

• GC/FID with 15 m × 0.53 mm × 0.5 μm 35% diphenyl stationary phase column
• Carrier gas hydrogen at 4 mL/min, injector at 275 °C in split mode
• Typical run time around 9 minutes for main cannabinoids

GC/MS Conditions for Confirmatory Analysis and Safety Testing

• 30 m × 0.25 mm × 0.25 μm column, helium carrier gas at 1.3 mL/min
• Splitless injection, mass range 50–400 m/z
• Extended analysis (~30 minutes) to include terpenoids and pesticide residues

Instrumentation Used

• Gas Chromatograph with Flame Ionization Detector (GC/FID)
• Gas Chromatograph coupled to Mass Spectrometer (GC/MS)
• Optional High Performance Liquid Chromatograph for acid cannabinoids and carbamate pesticides
• Headspace GC/FID for residual solvents measurement
• Inductively Coupled Plasma Mass Spectrometer (ICP-MS) for heavy metals

Key Results and Discussion

The selected intermediate polarity column resolves CBD from CBC and achieves clear separation of at least eight major cannabinoids within a 9–30 minute window depending on the method. GC/FID provides rapid quantification of decarboxylated THC and CBD, matching concentration levels in the 1–30% range. GC/MS offers higher specificity for positive identification, terpenoid profiling and pesticide screening. Method linearity aligns with typical sample concentrations around 500–700 μg/mL prior to dilution.

Benefits and Practical Applications

• Fast turnaround for routine potency testing using GC/FID
• Definitive compound identification and multi-residue safety screening with GC/MS
• Adaptable to flower, extracted oils, edibles and tinctures
• Compliance with evolving regulatory standards for THC/CBD ratios, pesticides and solvents

Future Trends and Opportunities

Advances are expected in ultra-fast chromatography, automated sample prep workflows and the integration of high-resolution mass spectrometry for trace contaminant detection. Regulatory harmonization will drive standardized protocols. Emerging focus on minor cannabinoids and terpenoid profiles will expand analytical scopes.

Conclusion

GC/FID and GC/MS provide robust platforms for comprehensive cannabis potency analysis. The combination of rapid quantification and confident compound identification meets both regulatory and market demands. Continued method development will enhance throughput, accuracy and multi-analyte capability.