Probe ESI Screening and Quantification for Drugs in Whole Blood Combined with Quadrupole Time-of-Flight Mass Spectrometer

Importance of the Topic

Rapid identification and quantification of drugs in whole blood are critical for forensic toxicology, clinical monitoring, and toxicology screening. Traditional LC–MS workflows often require extensive sample preparation and long run times. Innovative probe ESI techniques, such as direct probe ionization via DPiMS QT, enable streamlined workflows and faster turnaround, addressing increasing demands for efficient toxicology testing.

Study Objectives and Overview

This study introduces a qualitative and quantitative workflow combining DPiMS QT probe electrospray ionization with an upgraded Shimadzu quadrupole time-of-flight mass spectrometer. The primary aims are to demonstrate qualitative screening across positive and negative modes in a single run and to establish calibration and quantification protocols for seven representative drugs spiked in whole blood.

Methodology and Instrumentation

Sample Preparation:

• Seven drugs (amoxapine, clozapine, nortriptyline, pentobarbital, quetiapine, risperidone, salicylic acid) spiked into human whole blood at concentrations ranging 10–1000 ng/mL.
• Dilution protocol: 10 µL blood + 90 µL water + 100 µL isopropanol containing internal standards (diazepam-d5, phenobarbital-d5), followed by centrifugation and direct plating of 10 µL supernatant.

Applied Instrumentation:

• Probe ESI source: DPiMS QT for direct ionization.
• Mass spectrometer: Upgraded Shimadzu Q-TOF enabling rapid polarity switching, high mass stability, and iDIA (intelligent data-independent acquisition).
• Analytical conditions: m/z range 100–500, collision energy ramp 10–50 eV, desolvation temperature 250 °C, heat block 50 °C, interface voltages ±3.5/−2.5 kV.

Main Results and Discussion

• Qualitative Screening: iDIA acquired comprehensive MS/MS spectra in both polarities within ~2.9 min, delivering fragment patterns equivalent to conventional LC-ESI-Q-TOF workflows.
• Mass Accuracy: Mass errors for seven analytes at 1 µg/mL were within ±2.4 ppm in both modes, demonstrating excellent mass stability.
• Quantification: Calibration curves for all compounds showed strong linearity (R2 ≥ 0.99) across concentration ranges of 10–1000 ng/mL. Analysis time for combined polarities was under 1.1 min per sample group.

Benefits and Practical Applications

• Significant reduction in sample preparation and analysis time compared to traditional LC-MS methods.
• Single-run capability for both positive and negative ions simplifies workflows in forensic and clinical toxicology laboratories.
• High mass accuracy and comprehensive MS/MS data support reliable identification of multiple drug classes in complex matrices.

Future Trends and Opportunities

• Expansion of compound libraries for broader toxicological screening.
• Integration with automated sample handling for high-throughput applications.
• Development of portable probe ESI-QTOF systems for point-of-care or in-field toxicology testing.
• Advanced data processing algorithms for real-time identification and quantification.

Conclusion

The combination of DPiMS QT probe ESI with an upgraded Shimadzu Q-TOF mass spectrometer provides a rapid, accurate, and streamlined workflow for qualitative screening and targeted quantification of drugs in whole blood. This approach meets the growing needs of forensic and clinical toxicology by offering high throughput, simplified sample preparation, and reliable identification within minutes.

Reference

No references provided.