Rapid Detection of the Low Dose API in Xanax Using Surface-Enhanced Raman Spectroscopy for Anti-Counterfeiting Purposes

Significance of the Topic

Counterfeit prescription medications are a growing threat worldwide. Rapid, sensitive methods to detect low levels of active pharmaceutical ingredients (APIs) in tablets are essential to ensure patient safety and combat illicit drug distribution. Surface-enhanced Raman spectroscopy (SERS) offers enhanced signal detection that can reveal trace APIs at the surface of tablets, enabling field-based screening by law enforcement and pharmaceutical quality control.

Study Objectives and Overview

This study aims to develop a handheld SERS-based approach for detecting alprazolam at concentrations below 0.2% w/w in genuine Xanax tablets. A secondary objective is to differentiate authentic tablets from counterfeits containing fentanyl. The method utilizes a handheld Raman spectrometer with a SERS substrate to achieve rapid, non-destructive identification for anti-counterfeiting applications.

Used Instrumentation

• TacticID GP Plus handheld Raman spectrometer (785 nm excitation) for rapid non-destructive analysis
• TacticID N Plus handheld Raman spectrometer optimized for narcotics and pharmaceuticals
• TacPac SERS adapter and paper-based SERS substrates for enhanced signal collection

Methodology and Sample Preparation

The experimental protocol involves:

• Grinding approximately 30 mg of a genuine 0.25 mg alprazolam Xanax tablet
• Dissolving the powder in 0.5 mL acetone to extract surface API
• Immersing a paper-based SERS substrate in the solution for 30 s
• Positioning the substrate in the handheld spectrometer adapter
• Acquiring SERS spectra at a minimum of three distinct spots per substrate (integration 15–30 s)

Police-department–confirmed fentanyl samples were processed identically to evaluate method specificity.

Main Results and Discussion

Direct Raman measurements on tablet surfaces detected only excipient signals (e.g., lactose peaks at 356, 436, 476, 1088, 1120, 1264 cm⁻¹) with no alprazolam features. In contrast, SERS spectra revealed characteristic alprazolam peaks at 688, 1000, 1132, 1160, 1312, 1380, 1484, 1568, and 1592 cm⁻¹. Excipients showed negligible solubility in acetone and did not interfere with the API signal. Fentanyl SERS spectra displayed common ring-breathing peaks around 1000 and 1029 cm⁻¹ but lacked the unique alprazolam markers. A correlation-based Hit Quality Index (HQI) yielded average values of 91.0 for alprazolam and 82.3 for fentanyl, with no significant matches for excipients, demonstrating high selectivity and sensitivity.

Benefits and Practical Applications

• Rapid on-site verification of low-dose APIs in tablets for customs, law enforcement, and pharmaceutical QC
• Minimal sample preparation and non-destructive analysis preserve evidence integrity
• High selectivity distinguishes genuine tablets from dangerous fentanyl-laced counterfeits
• Portable, handheld instrumentation with onboard algorithms enables real-time decision making

Future Trends and Opportunities

• Integration of machine learning algorithms for automated spectral interpretation and anomaly detection
• Development of multiplexed SERS substrates to screen multiple APIs and adulterants simultaneously
• Miniaturization of Raman systems and smartphone interfaces for broader field deployment
• Expansion of spectral libraries to include new psychoactive substances and emerging counterfeit formulations
• Advancements in substrate design to further lower detection limits and improve signal reproducibility

Conclusion

The developed handheld SERS method reliably detects alprazolam at trace levels in Xanax tablets and distinguishes genuine products from fentanyl-based counterfeits. Its simplicity, portability, and rapid turnaround make it a valuable tool for anti-counterfeiting efforts in pharmaceutical security and law enforcement.

References

• U.S. Food and Drug Administration. Counterfeit Medicine. http://www.fda.gov/Drugs/ResourcesForYou/Consumers/BuyingUsingMedicineSafely/CounterfeitMedicine/
• Addiction Resource. The Dangers of Fentanyl. https://addictionresource.com/drugs/the-dangers-of-fentanyl/
• Drug Enforcement Administration. Counterfeit Prescription Pills. https://www.dea.gov/docs/Counterfeit%20Prescription%20Pills.pdf
• Xanax Official Website. https://www.xanax.com/
• National Institute on Drug Abuse. Drugs of Abuse: Fentanyl. https://www.drugabuse.gov/drugs-abuse/fentanyl