Determination of cannabinoids (THC) in urine samples with GC-MS

Importance of the topic

The reliable detection of THC and its metabolites in urine supports forensic toxicology clinical research workplace drug screening and therapeutic monitoring by providing key information on cannabis use patterns and exposure levels

Objectives and study overview

This work describes a streamlined GC-MS approach for quantifying total urinary cannabinoids by combining enzymatic hydrolysis liquid-liquid extraction and silylation to measure THC THC-OH and THC-COOH with high specificity and accuracy

Methodology and sample preparation

Hydrolysis and extraction

• Urine samples homogenized and spiked with standards and deuterated internal standards
• Enzymatic deconjugation using beta-glucuronidase at 37 °C overnight
• First liquid-liquid extraction under alkaline conditions with ethyl acetate n-hexane (9+1)
• Acidified secondary extraction to improve recovery of acidic metabolites
• Concentration under nitrogen at 40 °C and derivatization with MSTFA

Used instrumentation

Gas chromatograph Shimadzu GCMS-QP2010plus equipped with EI source operating in SIM mode

• Column Optima 5 HT 30 m×0.25 mm×0.25 μm
• Carrier gas helium splitless injection at 250 °C
• Oven program from 70 °C to 250 °C then to 300 °C
• Selected m/z transitions for analytes and D3 internal standards

Main results and discussion

Calibration curves displayed excellent linearity from 25 to 250 ng/mL with r2 values above 0.996. Representative chromatograms showed clear resolution of native cannabinoids and deuterated analogs in spiked urine. The sample preparation yielded clean extracts and reliable quantitation across the target range

Benefits and practical applications

The method offers simplicity efficiency and robust performance for forensic casework clinical monitoring workplace drug testing and pharmacokinetic studies. Use of deuterated internal standards ensures accurate correction for matrix effects and extraction variability

Future trends and opportunities

Implementation of solid phase extraction could enhance sensitivity and lower detection limits. Integration of high-resolution or tandem MS systems may improve selectivity. Automation and microfluidic platforms promise higher throughput and reduced solvent use. Expanded analyte panels will support more comprehensive drug monitoring applications

Conclusion

A rapid and reliable GC-MS protocol for total cannabinoid determination in urine has been established. The workflow combines enzymatic hydrolysis efficient extraction and MSTFA derivatization to achieve sensitive and reproducible quantitation suitable for various analytical settings

References

1 F Grotenhermen Clinical Pharmacokinetics of Cannabinoids Journal of Cannabis Therapeutics 2003
2 T Nadulski F Sporkert M Schnelle et al Journal of Analytical Toxicology 2005