Simultaneous Screening and Quantitation of Amphetamines in Urine by On-line SPE-LC/MS Method

Significance of the Topic

Amphetamines are stimulant drugs widely abused and controlled under drug testing guidelines.
Rapid and reliable quantification in urine is essential for forensic and clinical applications.

Objectives and Study Overview

This study aimed to develop a fully automated on-line SPE-LC/MS approach for simultaneous screening, confirmation, and quantitation of five amphetamines in urine.
It addresses new SAMHSA guidelines by including potential interferences and reference compounds to ensure identification reliability.

Methodology and Instrumentation

• Sample Preparation: Tenfold dilution of urine, no off-line cleanup.
• On-line SPE: Synergi Polar-RP trapping column (50×2 mm, 2.5 µm) with switching valve.
• Analytical Separation: Shim-pack VP-ODS column (150×2 mm, 5 µm), gradient elution with water/MeOH (0.1% formic acid).
• Detection: Shimadzu LCMS-2020 single quadrupole, ESI positive mode, SIM for quantitation and scan for confirmation.

Results and Discussion

• Recovery: 69.5–97.3% at 62.5 ppb, consistent across 250 and 500 ppb.
• Linearity: 2.5–500 ppb with R² > 0.99 for all compounds.
• Sensitivity: LOD 1.9–7.1 ng/mL and LOQ 5.7–21.7 ng/mL in source urine.
• Matrix Effects: 69–116% signal variation, acceptable for reliable quantitation.
• Precision: RSD 0.41–5.3% (n=6) at 62.5 ppb.
• Robustness: Consistent retention and response over 200 injections.
• Reliability: No false positives/negatives at 25 ng/mL level in various urine matrices.

Benefits and Practical Applications

This method streamlines workflow by eliminating derivatization and off-line cleanup, reduces analysis time, and enhances lab throughput.
It is particularly suited for high-volume forensic and clinical drug screening laboratories.

Future Trends and Opportunities

• Extension to additional controlled substances and metabolites.
• Integration with high-resolution MS for increased specificity.
• Development of miniaturized SPE sorbents for field-portable analysis.
• Automation in data processing and reporting for large-scale screening programs.

Conclusion

The developed on-line SPE-LC/MS method provides a sensitive, robust, and efficient solution for amphetamine analysis in urine, compliant with regulatory standards and suitable for routine laboratory use.

Reference

1. Kudo K, Ishida T, Hara K, et al. J Chromatogr B. 2007;855:115-120.
2. SAMHSA Manual for Urine Laboratories. US Department of Health and Human Services; 2010.