Exploring the Impact of Part Per Billion Mass Accuracy for Metabolite Identification Using Multi Reflecting Time-of-Flight MS With UPLC™ Part A

Significance of the Topic

A precise mass measurement at the part‐per‐billion level is essential for reliable small molecule and metabolite identification in complex biological samples. High mass accuracy reduces false positives and enhances confidence in non‐targeted screening workflows, supporting applications in clinical testing, toxicology, and pharmaceutical research.

Objectives and Study Overview

This study evaluates the impact of sub‐ppm mass accuracy on metabolite identification using a SELECT SERIES Multi Reflecting Time‐of‐Flight mass spectrometer coupled with UPLC‐MSE ES+. A non‐targeted data‐independent acquisition urinary screening was performed over four time points after dosing with acetaminophen, carbamazepine, and naproxen. System robustness and mass accuracy were assessed over a 24‐hour period.

Methodology and Instrumentation

Sample preparation involved 10:1 dilution of human urine collected at 0, 2, 4, and 6 hours post‐dose. UPLC separation was carried out on an ACQUITY UPLC I-Class Premier with an HSS T3 C18 column (100×2.1 mm, 1.8 µm) at 40 °C, 0.5 mL/min, gradient elution using 0.1% formic acid in water (A) and acetonitrile (B). Mass spectrometry used SELECT SERIES MRT in ES+ mode at 10 Hz, achieving >200,000 FWHM resolving power, capillary 0.5 kV, source 120 °C, desolvation 500 °C, collision energy 15–45 eV, m/z 50–2400. Data were processed with MassLynx v4.2 and waters_connect 3.1.

Main Results and Discussion

An RMS error of 549 ppb was obtained for 2651 detections, demonstrating routine ppb mass accuracy. High resolution DIA at 10 Hz provided >170,000 FWHM for carbamazepine at m/z 237.1 with 18 points across a 3.6 s peak. Major metabolites—including acetaminophen glucuronide and sulfate, carbamazepine‐10,11‐epoxide, hydroxylated and glucuronidated species, naproxen acyl glucuronides—were identified with mass errors typically <600 ppb. Fine isotope structure and high resolution fragment ions resolved matrix interferences. Time‐course response trends confirmed metabolite profiles.

Benefits and Practical Applications

• Enhanced identification confidence and reduced false detections
• Improved data analysis efficiency through stringent post‐processing mass filters
• Maintenance of chromatographic fidelity at high acquisition rates
• Routine ppb accuracy for both precursor and fragment ions
• Exploitation of fine isotope structure for unknown characterization

Future Trends and Opportunities

The integration of ultrahigh resolution MS data with advanced informatics and machine learning will further streamline non‐targeted workflows. Emerging applications include lipidomics, metabolomics, real‐time screening, and stable isotope‐resolved drug metabolism studies. Continued improvements in ion mobility and computational deconvolution will enhance specificity and throughput.

Conclusion

The UPLC‐MRT‐MS platform delivers routine ppb mass accuracy at 10 Hz without compromising chromatographic performance. This capability strengthens non‐targeted metabolite screening by reducing candidate elemental compositions, lowering false positive rates, and accelerating data interpretation for pharmaceutical and bioanalytical research.

Instrumentation

• Waters ACQUITY UPLC I-Class Premier
• ACQUITY UPLC HSS T3 C18 column (100×2.1 mm, 1.8 µm)
• SELECT SERIES Multi Reflecting TOF mass spectrometer
• MassLynx v4.2 software
• waters_connect 3.1

References

• Schymanski EL et al. Environ. Sci. Technol. 2014;48(4):2097–2098.
• FDA Guidance for Industry: Safety Testing of Drug Metabolites. CDER, 2008.
• Bradshaw PR et al. Drug Discov Today. 2020;25(9):1639–1650.
• Cooper‐Shepherd DA et al. J Am Soc Mass Spectrom. 2023;34(2):264–272.
• Vree TB et al. Biopharm Drug Dispos. 1993;14(6):491–502.