Quantitation of an Oral Fluid Drug Panel Including THC Using High Resolution Accurate-Mass (HRAM) Orbitrap Mass Spectrometry

Importance of the Topic

The analysis of drugs of abuse in oral fluid is gaining prominence in clinical, forensic and roadside testing due to its non-invasive collection and rapid turnaround. Meeting the stringent sensitivity and specificity requirements set by regulatory bodies such as SAMHSA and the National Safety Council ensures reliable detection of a broad panel of compounds, including challenging neutral analytes like THC.

Objectives and Study Overview

This study aimed to develop and validate a fast, robust method for the confirmation and quantitation of 31 drugs of abuse in human oral fluid. The target list matches the 2023 SAMHSA guidelines and NSC Tier 1 cutoffs, incorporating diverse drug classes from amphetamines to opioids and cannabinoids.

Methodology and Used Instrumentation

Sample preparation employed DPX INTip SCX/WAX solid-phase extraction to recover both basic and neutral compounds.

• UHPLC: Thermo Scientific Vanquish Horizon system with Accucore Vanquish Biphenyl column (2.6 µm, 50 × 2.1 mm).
• Chromatography: 7-minute gradient using 0.1% formic acid in water (A) and methanol (B).
• Mass spectrometry: Thermo Scientific Orbitrap Exploris 120 in full-scan and data-dependent MS2 (ddMS2) modes at 60 000 FWHM (MS1) and 15 000 FWHM (MS2).
• Data processing: Thermo Scientific TraceFinder 5.2 with a Compound Database for exact mass, retention time, isotopic pattern, fragment ions and library matching.

Main Results and Discussion

All 31 analytes achieved limits of quantitation (LOQs) lower than SAMHSA and NSC cutoffs, with linearity up to 1 000 ng/mL (5 000 ng/mL for select compounds). Recovery studies demonstrated consistent extractability (>60% recovery across the panel). The 7-minute UHPLC method resolved isomeric and co-eluting compounds, illustrated by combined extracted ion chromatograms. Challenges with THC adsorption were mitigated by using silanized glassware and organic modifiers throughout SPE and reconstitution. Representative calibration curves for THC and fentanyl at LOQ levels confirmed method accuracy and precision.

Benefits and Practical Applications

The developed workflow delivers rapid throughput and flexibility, allowing laboratories to

• Meet regulatory confirmation criteria (isotopic pattern, fragment ions, library match).
• Add or modify target analytes without altering the core protocol.
• Apply to roadside drug screening, clinical toxicology, and forensic investigations.

Future Trends and Opportunities

Advances may include automation of SPE for higher throughput, expanded high-resolution libraries for emerging psychoactive substances, integration of AI-driven data review, and enhanced extraction techniques for neutral or sticky compounds. Coupling multiplexed sampling devices with rapid HRAM workflows can further accelerate field testing.

Conclusion

This HRAM Orbitrap LC-MS method with DPX INTip SPE provides a validated, high-throughput solution for simultaneous quantitation of 31 drugs in oral fluid. It meets or exceeds SAMHSA and NSC requirements, offering clinical, forensic and roadside testing laboratories a reliable and adaptable assay.

References

No external literature references were provided in the source document.