Forensic Toxicology Data-Independent Analysis Screening Using Xevo MRT Mass Spectrometer Routine Parts-per-Billion (ppb) Mass Accuracy

Importance of Topic

Broad screening of complex biological matrices is essential in forensic toxicology to identify illicit and non‐illicit drugs rapidly and accurately. Data‐independent acquisition (DIA) with high‐resolution mass spectrometry enhances detection confidence while reducing false positives and resource use.

Objectives and Study Overview

This study aimed to demonstrate the benefits of routine parts‐per‐billion (ppb) mass accuracy for DIA screening using the Xevo MRT mass spectrometer. Ten anonymized urine samples and a commercial standard were analyzed to assess specificity, mass accuracy, and identification confidence.

Methodology and Instrumentation

A system suitability test mix at 25 ng/mL in 5 mM ammonium formate (pH 3) and diluted urine samples were separated by UPLC with a 15-minute gradient. Data were acquired in MSE mode using electrospray ionization positive mode on a Xevo MRT MS coupled to ACQUITY UPLC, processed with waters_connect informatics and a forensic library of over 2000 compounds.

Key Results and Discussion

• Precursor ions (m/z 122–478) achieved a root mean square mass error of 571 ppb, with 94 % detections within ±1 ppm.
• Fragment ions (m/z 80–268) for 92 fragments achieved 96 % detections within ±1 ppm and ±0.2 mDa.
• Adjusting fragment mass tolerance from 2 mDa to 0.2 mDa prevented false positives, as demonstrated for anabasine versus nicotine.
• High mass accuracy allows reliable identification by less experienced analysts and reduces confirmation workload.

Benefits and Practical Applications

• Enhanced specificity and selectivity facilitate rapid forensic screening in routine laboratories.
• Reduced false positives cut down the number of samples requiring confirmatory assays, lowering costs and turnaround time.
• Improved sustainability by minimizing consumable use and reliance on external outsourcing.

Future Trends and Opportunities

Advances in DIA coupled with sub‐ppm mass accuracy promise further improvements in screening throughput and sensitivity. Integration with expanded spectral libraries and machine learning algorithms could enable real‐time identification and quantification in diverse matrices.

Conclusion

Routine ppb mass accuracy with DIA on the Xevo MRT enhances forensic toxicology screening by increasing detection confidence, reducing false positives, and streamlining workflows, supporting timely and cost‐effective analyses.

Used Instrumentation

• ACQUITY UPLC I-Class FTN system
• Xevo MRT mass spectrometer operating in MSE mode with ESI positive ionization
• waters_connect informatics platform and forensic compound library

Reference

1. Mistry NS, Calton LJ, Cooper J. The Utility of MSE for Toxicology Screening with waters_connect and the Xevo G3 QTof Mass Spectrometer. Waters Application Note 720008045, September 2023.
2. Mistry NS, Calton LJ, Cooper J. The Ultimate Forensic Toxicology Screening Companion—Xevo G3 QTof. Waters Application Note 720008033, September 2023.