Rapid Analysis of Cocaine and Metabolites by Mixed-Mode μElution SPE Combined with UPLC-MS/MS

Significance of the Topic

The accurate and rapid detection of cocaine and its major metabolites in biological fluids is essential for forensic investigations, clinical toxicology, workplace drug testing, and anti-doping controls. Traditional workflows involving conditioning, evaporation, and reconstitution steps can be time-consuming and labor intensive. By integrating mixed-mode µElution solid-phase extraction with ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS), this method streamlines sample preparation while maintaining high sensitivity and reproducibility.

Objectives and Study Overview

This study aimed to develop and validate a rapid, simplified workflow for the extraction and quantification of cocaine, benzoylecgonine, and cocaethylene in urine samples. Key goals included eliminating conditioning and evaporation steps, reducing analysis time, and achieving linear, accurate, and precise results suitable for routine high-throughput applications.

Methodology and Instrumentation

Sample Preparation:

• Aliquot 200 µL urine, add 20 µL deuterated internal standard solution and 200 µL 4 % H₃PO₄.
• Load directly onto Oasis MCX µElution plate by vacuum.
• Wash sequentially with 200 µL 2 % formic acid in water and 200 µL methanol.
• Elute twice with 25 µL 60:40 acetonitrile:methanol containing 5 % strong ammonia and dilute with 40 µL 2 % formic acid in water.

Chromatographic Conditions:

• System: ACQUITY I-Class UPLC
• Column: ACQUITY UPLC HSS T3, 2.1 × 50 mm, 1.8 µm, 30 °C
• Mobile phases: Water/0.1 % formic acid (A) and acetonitrile/0.1 % formic acid (B)
• Gradient: 98 % A initial, ramp to 43 % A at 3 min, return to initial at 3.1 min, total run time 4 min

Instrumentation

• Oasis MCX µElution 96-well plate
• ACQUITY I-Class UPLC System
• ACQUITY UPLC HSS T3 Column, 100 Å, 1.8 µm, 2.1 × 50 mm
• Xevo TQD Triple Quadrupole Mass Spectrometer (ESI+)

Results and Discussion

All analytes eluted within 3 minutes with peak widths below 3 seconds. Recoveries ranged from 83 % to 105 % (RSD ≤ 6.9 % for cocaine and cocaethylene; ≤ 13.8 % for benzoylecgonine). Matrix effects were minimal (average –15 % for cocaine and cocaethylene; +3 % for benzoylecgonine; SD ≤ 1.2 %). Calibration curves were linear over 1–1000 ng/mL (R² ≥ 0.99) with mean deviations ≤ 6.7 %. QC samples at low, mid, and high levels demonstrated accuracies within ±10 % and precision (RSD) ≤ 7 %.

Benefits and Practical Applications

• Eliminates conditioning, equilibration, evaporation, and reconstitution steps
• Shortened sample preparation and analysis times (≤ 4 min per run)
• High throughput suitable for forensic, clinical, and anti-doping labs
• Robust performance with minimal matrix interference

Future Trends and Opportunities

Further integration of µElution SPE with automated liquid-handling platforms can enhance throughput. Expansion to comprehensive drug panels and incorporation of high-resolution mass spectrometry could improve selectivity and enable retrospective data analysis. Miniaturization and green-chemistry approaches will continue to drive sustainable practices in bioanalysis.

Conclusion

The presented µElution SPE coupled with UPLC-MS/MS method offers a rapid, streamlined, and reliable approach for quantifying cocaine and key metabolites in urine. High recovery, low matrix effects, and excellent linearity, accuracy, and precision make it well suited for routine forensic and clinical applications.

References

1. Isenschmid D. Cocaine. In Principles of Forensic Toxicology; Levine B., Ed.; AACC Press: Washington, D.C., 2013; pp. 293–315.
2. National Institute on Drug Abuse. NIDA Research Report Series: Cocaine, 2008.
3. BuddyMD. Benzoylecgonine (Cocaine) Drug Elimination Time and Clearance.
4. PubMed. PMID: 1432406.