Quantitative Analysis of THC and its Metabolites in Plasma Using Oasis PRiME HLB for Toxicology and Forensic Laboratories

Significance of the topic

Forensic toxicology demands rapid and accurate analysis of psychoactive compounds in biological fluids. Plasma is often the matrix of choice for pharmacokinetic and clinical studies due to its consistency compared to whole blood. Reliable quantification of THC and its metabolites underpins legal decisions, clinical monitoring, and research on cannabis effects.

Objectives and Study Overview

This application note evaluates a streamlined workflow combining Oasis PRiME HLB μElution plates with UPLC-MS/MS for the extraction and quantification of Δ9-THC, 11-hydroxy-THC (THC-OH), and 11-nor-9-carboxy-THC (THC-COOH) in human plasma. Key goals include simplifying sample preparation, minimizing matrix effects, and achieving high throughput with robust analytical performance.

Methodology

• Protein precipitation: 200 µL 0.1% formic acid in acetonitrile added to 100 µL plasma, vortexed and centrifuged.
• SPE cleanup: Direct loading onto Oasis PRiME HLB μElution plate without conditioning or equilibration; wash with 2×250 µL 25:75 methanol:water; elution in 2×25 µL 90:10 acetonitrile:methanol; dilute with 50 µL water; inject 5 µL.
• UPLC separation: ACQUITY UPLC BEH C18 column (2.1×50 mm, 1.7 µm) at 40 °C; gradient from 50/50 to 5/95 water/acetonitrile (0.1% formic acid) in 3 minutes.
• MS detection: Xevo TQ-S triple quadrupole in ESI positive mode; optimized MRM transitions for each analyte and deuterated internal standard; data acquired with MassLynx and quantified with TargetLynx.

Instrumentation

• Oasis PRiME HLB μElution 96-well plate
• ACQUITY UPLC I-Class system with BEH C18 column
• Xevo TQ-S triple quadrupole mass spectrometer
• MassLynx v4.1 and TargetLynx software

Main Results and Discussion

• Chromatography: All analytes elute in under 3 minutes with peak widths <3 s and asymmetry 0.95–1.15.
• Recovery: 78–86% with RSD <6%.
• Matrix effects: <20% ion suppression with RSD <3%.
• Linearity: 0.1–100 ng/mL, r2>0.997 (1/x weighting).
• Sensitivity: LLOQ of 0.1 ng/mL meets regulatory criteria.
• QC performance: Accuracy within 90–107%, precision RSD 2–5% across low to high levels.
• Phospholipid removal: >99% elimination compared to simple protein precipitation, reducing fouling and ion suppression.

Benefits and Practical Applications

• Simplified workflow with no sorbent conditioning, equilibration, evaporation or reconstitution.
• High throughput enabled by μElution format and direct injection.
• Cleaner extracts extend column and source lifetimes, reduce maintenance.
• Applicability to forensic casework, clinical trials, doping control, and therapeutic monitoring.

Future Trends and Potential Applications

• Expansion to multi-analyte panels covering a broader range of drugs and biomarkers.
• Automation of sample preparation for increased throughput.
• Integration with high-resolution mass spectrometry for untargeted screening.
• Adoption in roadside testing and clinical settings for therapeutic cannabinoid monitoring.

Conclusion

The combination of Oasis PRiME HLB μElution plates and UPLC-MS/MS delivers a rapid, sensitive, and reproducible method for the quantification of THC and its metabolites in plasma. The streamlined protocol meets the rigorous demands of modern forensic and clinical laboratories by providing high recovery, low matrix effects, and robust analytical performance.

References

1. Farrell LJ, Kerrigan S, Logan BK. Recommendations for Toxicological Investigation of Drug Impaired Driving. J Forensic Sci. 2007;52(5):1214–1218.
2. Elian AA, Hackett J. Solid-Phase Extraction and Analysis of THC and Carboxy-THC from Whole Blood Using a Novel Fluorinated SPE Sorbent and Fast LC-MS/MS. J Anal Toxicol. 2009;33(8):461–468.
3. Schwilke EW, Karschner EL, Lowe RH, et al. Intra- and Intersubject Whole Blood/Plasma Cannabinoid Ratios Determined by 2D EI GC-MS with Cryofocusing. Clin Chem. 2009;55(6):1188–1195.
4. Lee D, Bergamaschi MM, Milman G, et al. Plasma Cannabinoid Pharmacokinetics After Controlled and Ad libitum Cannabis Smoking in Chronic Frequent Users. J Anal Toxicol. 2015;39(8):580–587.
5. Milman G, Bergamaschi MM, Lee D, et al. Plasma Cannabinoid Concentrations During Dronabinol Pharmacotherapy for Cannabis Dependence. Ther Drug Monit. 2014;36(2):218–224.
6. Huestis MA, Henningfield JE, Cone EJ. Blood Cannabinoids I. Absorption of THC and Formation of 11-OH-THC and THCCOOH During and After Smoking Marijuana. J Anal Toxicol. 1992;16(5):276–282.