Screening in Equine Doping Control Analysis with Ultrahigh Resolution and Accurate Mass

Significance of the Topic

Equine doping control is critical to ensure animal welfare and fair competition in horse racing. Rapid, reliable screening methods capable of detecting a wide range of prohibited substances in complex urine matrices support regulatory compliance and scientific confidence. High resolving power and accurate mass analysis address key challenges such as data re-interrogation, high throughput, and interference separation.

Objectives and Study Overview

This study demonstrates a novel approach for comprehensive screening of over 120 illicit compounds (including steroids, anti-inflammatories, anesthetics, and diuretics) in equine urine. Using ultrahigh resolution (>50,000 FWHM) and accurate mass measurements in both positive and negative ion modes, the work aims to streamline method development, facilitate data review, and improve identification confidence.

Methodology and Instrumentation

Sample Preparation:

• Enzymatic hydrolysis: hydrocortisone d3 spike, phosphate buffer, β-glucuronidase and protease, 55 °C incubation, centrifugation
• SPE cleanup: C18 cartridge conditioned with methanol and water, sample loading, water and hexane wash, dichloromethane/ethanol elution, evaporation, reconstitution in water/acetonitrile (80/20)

Chromatography:

• Shimadzu binary pumps LC-20ADxr
• Reversed-phase C18 column (3.5 µm, 150 x 2.1 mm)
• Mobile phases: 0.1% formic acid in water (A) and acetonitrile (B)
• Flow rate: 0.3 mL/min; injection volume: 10 µL; gradient from 80%A/20%B to 100%B over 25 min

Instrumentation Used

• Thermo Scientific Exactive benchtop LC/MS with Orbitrap technology
• Electrospray ionization with polarity switching (±4500 V/−3900 V)
• Resolution 50,000 FWHM; AGC target 5e5; capillary temperature 300 °C

Results and Discussion

The method achieved detection limits down to 50 pg/mL for corticosteroids and 1 ng/mL for triamcinolones with 5 ppm mass accuracy. Full MS acquisition facilitated retrospective analysis of non-targeted metabolites. Over 1,000 real urine samples were successfully screened, demonstrating robust performance. Representative extracted ion chromatograms confirmed accurate retention times and mass assignments for dexamethasone, flumethasone, triamcinolone acetonide, and triamcinolone.

Benefits and Practical Applications

• High confidence in compound identification via exact mass and retention time
• Efficient method development and instrument operation
• Extensive compound library screening in a single analysis
• Data re-interrogation capability enables discovery of new or unexpected analytes

Future Trends and Potential Applications

Advances in high-resolution mass spectrometry will drive broader untargeted screening and metabolomic profiling in veterinary and human doping control. Integration with machine learning for automated data interpretation and real-time decision support will further enhance analytical throughput. Miniaturized HRMS instruments may enable on-site screening at racetracks.

Conclusion

The Exactive high performance LC/MS system delivers ultrahigh resolution, precise mass accuracy, and fast full-scan acquisition for routine equine doping control. It supports comprehensive screening, confident identification, and retrospective data review, representing a significant advance in forensic toxicology workflows.

Reference

No literature references were provided in the original document.