Quantitation of an oral fluid drug panel including THC using the new Stellar mass spectrometer

Significance of the Topic

Oral fluid has emerged as a preferred matrix for roadside and workplace drug testing due to its noninvasive collection and reduced risk of tampering.
Reliable quantitation of a broad range of substances including neutral cannabinoids like THC alongside basic drugs poses analytical challenges.
Achieving low limits of quantitation in a rapid assay supports compliance with updated SAMHSA guidelines and National Safety Council Tier 1 cutoffs.

Study Objectives and Overview

This study aimed to develop a comprehensive workflow for confirming and quantitating 31 drugs of abuse in oral fluid within a 4.5-minute UHPLC run.

• Simultaneous extraction of neutral and basic analytes, particularly THC, using offline solid phase extraction.
• Attaining sensitivity and reproducibility that meet or exceed new regulatory cutoffs.
• Implementing automation to streamline sample preparation on a robotic platform.

Methodology and Instrumentation

An offline dispersive SPE protocol employed DPX XTR mixed mode SCX/WAX INTips on a Hamilton STAR automated liquid handler, reducing preparation time to under 45 minutes.
Chromatographic separation used a Vanquish Horizon UHPLC system with an Accucore Biphenyl column and a 4.5-minute gradient of 0.1% formic acid in water and methanol.
Detection was performed on a Stellar mass spectrometer in full scan plus targeted MS2 mode, utilizing both CID and HCD fragmentation and an OptaMax Plus HESI source at 500 °C vaporizer temperature.

Main Results and Discussion

Limits of quantitation ranged from 0.25 ng/mL for fentanyl to 1 ng/mL for THC, all below SAMHSA confirmation cutoffs and Tier 1 thresholds.
Isomeric pairs such as codeine/hydrocodone and morphine/hydromorphone achieved clear separation within the 4.5-minute run.
Ion ratio tolerances of ±20% and low percentage RSD values across triplicate calibrators confirmed method reproducibility.
Dual fragmentation modes allowed optimization of product ions, notably improving buprenorphine detection via CID over HCD.

Benefits and Practical Applications

• High-throughput analysis with a 4.5-minute cycle per sample.
• Automated SPE reduces hands-on time and enhances consistency.
• Enhanced sensitivity and selectivity ensure compliance with stringent cutoffs.
• Versatile fragmentation options maximize compound identification confidence.

Future Trends and Opportunities

Expanding panels to include emerging psychoactive substances and metabolite markers.
Integration of portable or on-site mass spectrometry for immediate roadside testing.
Adoption of microextraction and nano-LC approaches to minimize sample volume and accelerate analysis.
Application of AI-driven data interpretation for automated toxicological profiling.

Conclusion

A rapid, sensitive, and robust workflow for 31 drugs of abuse in oral fluid was demonstrated using automated SPE, ultra-high performance LC separation, and Stellar MS detection.
The method meets current regulatory requirements with excellent reproducibility and throughput, making it highly suitable for forensic and roadside toxicology applications.

Reference

• SAMHSA Center for Substance Abuse Prevention Oral Fluid Specimen Collection Handbook for Federal Agency Workplace Drug Testing Programs 2023.
• D’Orazio AL, Mohr ALA, Chan-Hosokawa A, et al. Recommendations for Toxicological Investigation of Drug-Impaired Driving and Motor Vehicle Fatalities – 2021 Update. Journal of Analytical Toxicology. 2021;45(6):529–536.