Detection of Cocaine in Seized Drug Samples by Capillary Electrophoresis Tandem Mass Spectrometry

Significance of the Topic

Rapid and reliable detection of cocaine in seized drug samples is critical for forensic investigations, public safety, and preventing accidental overdoses caused by variable purity levels.

Objectives and Study Overview

The study aimed to develop and validate a fast, sensitive capillary electrophoresis–tandem mass spectrometry (CE-MS/MS) method for quantifying cocaine in illicit samples. The approach focused on combining high separation efficiency with mass spectrometric selectivity to meet forensic requirements.

Methodology and Used Instrumentation

Sample Preparation:

• Homogenization of seized material.
• Extraction in methanol:water (50:50, v/v).
• Filtration through 0.45 µm regenerated cellulose membrane.

Capillary Electrophoresis Conditions:

• Instrument: Agilent 7100 CE system.
• Background electrolyte: 30 mM ammonium formate, pH 6.5.
• Fused-silica capillary (50 µm i.d., 75 cm total length).
• Applied voltage: 25 kV; temperature: 25 °C.
• Hydrodynamic injection: 12 s at 100 mbar.

Mass Spectrometry Conditions:

• Instrument: Agilent 6430 Triple Quadrupole LC/MS.
• Ionization: ESI in positive mode.
• Sheath liquid: 5 mM ammonium formate:methanol (50:50, v/v), pH 6.5.
• MRM transitions: m/z 304→182 (quantifier), 304→82 (qualifier).
• Drying gas: N₂ at 8 L/min, 180 °C; capillary voltage: 3,000 V.

Main Results and Discussion

• Separation achieved in 4 minutes with baseline resolution of cocaine and related alkaloids.
• Calibration linear over 0.02–1 µg/mL (R² > 0.999).
• Limit of detection (LOD): 0.003 µg/mL; limit of quantification (LOQ): 0.01 µg/mL.
• Repeatability (intra- and interday RSD) below 6.5%.
• Analysis of 11 seized samples detected cocaine in 93% of cases, with concentrations from 0.04 to 429 mg/g.
• Minor alkaloids (cinnamoylcocaine, tropacocaine) co-detected, supporting sample comparison and profiling.

Benefits and Practical Applications

• Fast turnaround (<5 min per sample) and minimal solvent consumption.
• High selectivity from MRM detection ensures low false positives.
• Meets SWGDRUG Class A and B confirmation criteria in a single run.
• Environmentally friendly due to low waste generation.

Future Trends and Potential Applications

• Extension to other illicit drugs and multi-residue forensic screening.
• Automation and high-throughput workflows for large-scale casework.
• Integration with data-mining platforms for source attribution and intelligence.
• Miniaturization and on-site CE-MS/MS systems for rapid field analysis.

Conclusion

The validated CE-MS/MS method delivers rapid, sensitive, and reliable cocaine quantification in seized drug samples. Its high selectivity, precision, and compliance with forensic standards make it a powerful tool for law enforcement and toxicology laboratories.

References

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