Using UPLC-MS/MS for the Determination of cTHC in Preserved Oral Fluid

Význam tématu

The analysis of 11-nor-9-carboxy-Δ-9-tetrahydrocannabinol (cTHC) in oral fluid offers a direct indicator of recent cannabis intake, enhancing the accuracy of forensic and roadside drug testing. Oral fluid sampling is non-invasive, reduces privacy and adulteration concerns compared to urine and does not require medically trained personnel like blood collection. Achieving reliable detection at low picogram-per-milliliter levels is crucial for confirming active cannabis consumption and distinguishing it from passive environmental exposure.

Cíle a přehled studie / článku

The primary objective was to develop and validate a simple, sensitive, and robust UPLC-MS/MS method capable of quantifying cTHC in preserved oral fluid at concentrations down to the low pg/mL range. This method is intended to support forensic toxicology and roadside drug testing schemes by providing confirmation analysis with high specificity and throughput.

Použitá metodika a instrumentace

A commercially available oral fluid collection device (Quantisal) was used to collect and stabilize 1 mL of oral fluid, resulting in a four-fold dilution upon buffering. Samples were stored at 4 °C for at least 24 hours prior to analysis. Cannabinoid extraction employed a liquid-liquid protocol: organic phase evaporation followed by reconstitution in 50% acetonitrile. Separation and detection were performed on an ACQUITY UPLC I-Class system coupled to a Xevo TQ-S micro tandem quadrupole mass spectrometer. A CORTECS C18 column provided chromatographic resolution, and two MRM transitions were monitored for cTHC (343.2>245.2 quantifier and 343.2>191.1 qualifier). The deuterated internal standard cTHC-d3 (346.2>248.2) ensured accurate quantitation. A 25 µL injection volume was used to maximize sensitivity.

Hlavní výsledky a diskuse

Comparison of blank and spiked oral fluid extracts at an equivalent of 20 pg/mL in neat fluid demonstrated clear chromatographic peaks with high signal-to-noise ratios for both MRM transitions. The method achieved reliable detection and quantification well below 20 pg/mL, with consistent qualifier-to-quantifier ratios, indicating strong selectivity in the complex oral fluid matrix. Chromatographic peak shapes were sharp and reproducible, and the overall workflow showed minimal matrix interferences.

Přínosy a praktické využití metody

• Non-invasive and supervised sample collection enhances chain of custody and reduces contamination risks.
• High analytical sensitivity enables detection of cTHC at low pg/mL levels for accurate confirmation of active use.
• Robust liquid-liquid extraction and standardized internal standardization yield reproducible results.
• Applicability in forensic laboratories and roadside testing centers for rapid confirmation analysis.

Budoucí trendy a možnosti využití

Future developments may include automated on-line sample preparation to increase throughput, multiplexed assays targeting multiple drug classes in a single run, and integration with portable or miniaturized mass spectrometers for field deployment. Advances in data processing and machine learning could further improve detection limits and automate result interpretation.

Závěr

The described UPLC-MS/MS method delivers simple, sensitive, and reliable quantification of cTHC in preserved oral fluid at low pg/mL concentrations. Utilizing readily available collection devices and established instrumentation, the protocol meets the demanding requirements of forensic and roadside drug testing, offering high specificity, reproducibility, and throughput.

Reference

• Lee R., Wood M. Using UPLC-MS/MS for the Determination of cTHC in Preserved Oral Fluid. Waters Corporation Technology Brief, 2017.