Assessing the Impact of Part-per-Billion Mass Accuracy Upon Forensic Toxicology Data-Independent Analysis Screening

Significance of the Topic

The accurate and rapid identification of drugs and toxicants in complex biological samples is critical for forensic investigations. High-resolution data-independent acquisition (DIA) workflows paired with parts-per-billion (ppb) mass accuracy can enhance selectivity, minimize false positives and reduce analytical turnaround times, supporting both operational efficiency and environmental sustainability.

Objectives and Study Overview

This study evaluated the impact of applying routine ppb mass accuracy tolerances on forensic toxicology screening. Using a commercial standard and anonymized urine samples, the work demonstrates how tightened precursor and fragment ion tolerances improve analyte confidence in DIA workflows on a Xevo MRT Mass Spectrometer.

Methodology and Instrumentation

• Samples
  • Commercial system suitability test mix at 25 ng/mL in 5 mM ammonium formate pH 3
  • Ten anonymized urine samples diluted 1:10 in mobile phase
• Instrumental Setup
  • Waters ACQUITY UPLC I-Class FTN PLUS coupled to Xevo MRT MS
  • MSE mode in electrospray ionization positive
  • 15-minute gradient separation
• Data Processing
  • Processed with waters_connect informatics library of >2000 drugs and metabolites
  • Applied precursor mass tolerance ≤2 ppm and fragment ion tolerance ≤0.2 mDa

Key Results and Discussion

• Precursor Mass Accuracy
  • 160 compounds (m/z 122–478) detected in ten urine samples
  • Root mean square error of 571 ppb
  • 94 % of precursors within ±1 ppm
• Fragment Ion Accuracy
  • 92 fragments (m/z 80–268) from 23 analytes
  • 96 % of fragments within ±1 ppm at tolerance ≤0.2 mDa
• False Positive Prevention
  • Example of Anabasine misassignment at fragment tolerance ≤2 mDa
  • Tightening to ≤0.2 mDa removed spurious fragment and correctly assigned Nicotine

Benefits and Practical Applications

• Enhanced specificity reduces false positives and streamlines data review
• Enables less-experienced analysts to work independently and confidently
• Cost savings by lowering repeat analyses, consumable use and outsourcing fees
• Reduced environmental footprint through fewer confirmations and shorter instrument time

Future Trends and Potential Applications

• Further tightening of mass tolerances leveraging advances in detector technology
• Integration of automated workflows and AI-driven data processing for rapid flagging
• Expansion of comprehensive libraries to include new psychoactive substances and metabolites
• Application to other matrices such as blood, oral fluid and tissue extracts

Conclusion

This work demonstrates that routine ppb-level mass accuracy in DIA screening significantly improves analyte identification confidence in forensic toxicology. The approach delivers high specificity, faster turnaround and cost-effective workflows, supporting both investigative and sustainability goals.

References

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