Evaluation of an Ultrafast Online SPE/TOF System to Screen for Drugs of Abuse in Forensic

Importance of the Topic

Rapid and reliable drug screening is essential in forensic toxicology laboratories facing increasing sample loads and demand for fast turnaround. Traditional immunoassay and confirmatory GC/MS or LC/MS workflows often create bottlenecks. An ultrafast online SPE coupled with time-of-flight mass spectrometry (SPE/TOF) offers the potential to screen a broad range of drug classes in a single injection with cycle times under 15 seconds, while retaining sensitivity and specificity comparable to conventional LC/MS/MS.

Objectives and Study Overview

This study evaluated the performance of an online SPE/TOF system for simultaneous screening of multiple drugs of abuse in urine. Key goals included:

• Assess linearity and reproducibility across different drug classes.
• Determine cutoff thresholds and compare screening results to LC/MS/MS reference data.
• Validate cycle times and throughput for high-volume forensic applications.

Methodology and Instrumentation

Drug-free human urine was spiked with panels of analytes, treated with glucuronidase when required, diluted, and injected (10 µL) onto an Agilent RapidFire SPE interface. Two generic SPE methods were configured for broad drug panels and benzodiazepine-specific screening. Eluted compounds were analyzed on an Agilent 6550 QTOF in MS mode (100–1000 m/z, 2 GHz extended dynamic range, 3 spectra/s). Data processing utilized MassHunter Quantitative Analysis software.

Instrumentation Used

• Agilent RapidFire high-throughput SPE system with C and A2 cartridges
• Agilent 6550 quadrupole time-of-flight mass spectrometer
• Mobile phases: water with formic and trifluoroacetic acid, acetonitrile mixes, methanol/isopropanol blends
• MS parameters: gas temperature 200–350 °C, sheath gas flow 11 L/min, capillary voltage 3500 V, nozzle voltage 500 V

Main Results and Discussion

Screening panels including gabapentin, pregabalin, tramadol, carisoprodol, methadone/EDDP, PCP, 6-MAM, benzoylecgonine and amphetamines exhibited excellent linearity (R2 > 0.995) over cutoff ranges of 5–5000 ng/mL. Single-injection cutoff samples repeatedly met accuracy within 15% and coefficient of variation below 10%. A benzodiazepine panel (nordiazepam, alpha-hydroxyalprazolam, 7-aminoclonazepam, oxazepam, lorazepam, temazepam) at 50 ng/mL cutoff showed 100% concordance with LC/MS/MS. In blinded tests with 48 to 96 human urine samples, positives and negatives were correctly identified above or below thresholds, with minimal carryover and clear result visualisation.

Benefits and Practical Applications

The ultrafast SPE/TOF workflow delivers:

• High throughput (cycle times <15 s/sample) for large-scale forensic screening
• Sensitivity and specificity on par with LC/MS/MS confirmation
• Broad multi-class drug coverage in a single run
• Reduced reagent consumption and simplified sample preparation

This approach is suited for forensic laboratories, clinical toxicology screening, and quality control in pharmaceutical settings.

Future Trends and Opportunities

Further development may include expanding the analyte library to cover emerging designer drugs, integrating automated data review with advanced software algorithms, adapting protocols for alternative matrices (blood, oral fluid), and combining SPE/TOF with high-resolution and ion mobility separations. Ongoing optimization could improve limits of detection and enable point-of-care drug screening applications.

Conclusion

The evaluated ultrafast online SPE/TOF system achieves rapid, accurate, and precise screening of diverse drug classes in urine with exceptional throughput. It bridges the gap between high-capacity screening and confirmatory mass spectrometry, offering forensic laboratories a powerful tool to streamline workflows without compromising analytical performance.