Quantitative Determination of Drugs of Abuse in Human Whole Blood by LC/MS/MS Using Agilent Captiva EMR—Lipid Cleanup

Significance of the Topic

Accurate and rapid quantification of drugs of abuse in whole blood is critical in forensic toxicology. Blood provides early detection before metabolism, homogeneous distribution, and is legally mandated in many jurisdictions. However, complex matrices and high phospholipid content can compromise LC/MS/MS performance and increase instrument downtime.

Objectives and Study Overview

This study demonstrates the application of Agilent Captiva EMR-Lipid 96-well plates combined with in-well protein precipitation for the quantitative determination of 24 representative drugs of abuse in human whole blood by LC/MS/MS. The aim was to streamline sample preparation, maximize phospholipid removal, and validate method performance under high-throughput conditions.

Methodology and Used Instrumentation

• Sample preparation: 100 µL whole blood per well with in-well protein precipitation using cold 95:5 MeOH/ACN containing 1% NH4OH, followed by lipid cleanup with Captiva EMR-Lipid sorbent.
• Elution: primary elution by centrifugation or positive pressure, secondary wash with 80:20 ACN/water; evaporation and reconstitution in 20:80 ACN/5 mM ammonium acetate.
• LC/MS/MS setup: Agilent 1290 Infinity LC (binary pump, autosampler, column compartment) coupled to Agilent 6490 triple quadrupole with Jet Stream iFunnel ESI source using dMRM in positive mode.
• Chromatography: Poroshell 120 EC-C8, 100×2.1 mm, 2.7 µm column at 60 °C, 0.5 mL/min, 6 min gradient.

Main Results and Discussion

Validation over three days produced linear calibration curves (R2 > 0.995) across 0.1–20 ng/mL (0.5–20 ng/mL for select analytes), LOQs of 0.1 ng/mL (0.5 ng/mL where noted), accuracy within 100 ± 20%, and precision (RSD < 15%). Absolute recoveries averaged 60–90% for most compounds. EMR-Lipid cleanup removed over 99% of phospholipids, significantly reducing matrix effects, sample carryover, and system contamination. Both centrifugation and positive-pressure elution yielded comparable performance.

Benefits and Practical Applications

• High throughput: 96 samples prepared within two hours.
• Automatable 96-well format minimizing manual handling.
• Enhanced data reliability and extended instrument uptime through robust cleanup.
• Applicability in forensic, clinical, and QA/QC laboratories for reliable blood-based drug quantification.

Future Trends and Potential Applications

Advances in sorbent technology and integration with automated platforms will further simplify workflows and improve cleanup efficiency. Extending EMR-Lipid protocols to additional matrices (e.g., plasma, tissue) and coupling with high-resolution or ambient MS techniques may enable near-real-time on-site forensic and clinical testing.

Conclusion

The combined in-well protein precipitation and Captiva EMR-Lipid cleanup method delivers a streamlined, high-throughput LC/MS/MS workflow for quantifying drugs of abuse in whole blood. It achieves excellent sensitivity, accuracy, and precision while dramatically reducing matrix interferences and instrument maintenance.

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