Screening and semi-quantification of fentanyls in human urine using high-resolution Orbitrap mass spectrometry for clinical research or forensic toxicology

Importance of the topic

Fentanyl and its analogs are highly potent synthetic opioids widely used in anesthesia and pain management, but also misused as recreational drugs. Their extreme potency, with some analogs up to 10,000 times stronger than morphine, poses serious risks including respiratory depression and fatal overdose. Rapid and reliable screening of these substances in biological matrices is critical for clinical research, forensic toxicology, and public health monitoring.

Objectives and study overview

This work aimed to develop and validate a fast, sensitive method for screening and semi-quantification of fourteen fentanyl analogs in human urine. Key goals included minimal sample preparation, reliable identification at cutoff levels, and semi-quantitative performance around regulatory thresholds, using high-resolution Orbitrap mass spectrometry.

Methodology and instrumentation

Sample preparation involved centrifugation of urine, dilution with water containing stable-isotope internal standards, and direct injection of 10 µL into an LC-MS system.

Chromatography was performed on a Waters Acquity UPLC BEH C18 column (2.1×100 mm, 1.7 µm) at 40 °C with a gradient of water/0.1% NH4OH (A) and methanol (B). Flow rates transitioned from 0.6 mL/min to 0.4 mL/min during analyte elution and back to 0.6 mL/min for re-equilibration.

Detection used a Thermo Scientific Q Exactive Focus hybrid quadrupole-Orbitrap mass spectrometer with heated electrospray ionization in positive mode. A full-scan/data-dependent MS/MS (dd-MS2) workflow employed an inclusion list of monoisotopic masses and retention time windows to trigger fragmentation for confirmation.

Used instrumentation

• Thermo Scientific Q Exactive Focus Hybrid Quadrupole-Orbitrap Mass Spectrometer
• Thermo Scientific UltiMate 3000 RSLC System
• Waters Acquity UPLC BEH C18 Column (2.1×100 mm, 1.7 µm)
• Milli-Q Water Purification System

Main results and discussion

Validation around the lower limit of quantitation (LLOQ) demonstrated:

• Accuracy between 80.9% and 107.6% at cutoff levels for all analytes.
• Intra- and inter-assay precision (%CV) below 13.4% across analogs.
• Moderate matrix effects from ten individual urine sources, with %CV below 20% and maximum deviation under 30%.
• Linear response demonstrated in two ranges spanning LLOQ to high concentrations, suitable for semi-quantification.
• All fourteen fentanyl analogs were unambiguously identified at LLOQ by accurate mass (<±5 ppm), retention time, and MS/MS spectral matching against an mzVault library.

Benefits and practical applications

This method offers a rapid, high-throughput screening workflow with minimal offline sample handling, allowing direct injection of diluted urine. It supports forensic toxicology and clinical research by providing reliable semi-quantitative data for multiple fentanyl analogs at relevant cutoff levels. The inclusion of stable-isotope standards improves accuracy and compensates for matrix variability.

Future trends and applications

Advances in high-resolution mass spectrometry will allow expansion of screening panels to emerging novel psychoactive opioids. Integration of automated data analysis, larger spectral libraries, and targeted quantitative confirmation will enhance throughput and confidence. Combining this workflow with ambient ionization techniques or microfluidic sample prep could further reduce analysis time.

Conclusion

The developed Orbitrap-based method enables fast, sensitive screening and semi-quantification of fourteen fentanyl analogs in human urine with robust analytical performance at cutoff levels. Its ease of use and reliable identification make it well suited for forensic and clinical laboratories.

Reference

Olin M., Zheng Y. Screening and semi-quantification of fentanyls in human urine using high-resolution Orbitrap mass spectrometry. Thermo Fisher Scientific Technical Note TN73391, 2020.