Detecting fentanyl analogs in counterfeit pharmaceuticals by surface-enhanced Raman spectroscopy using handheld Raman spectrometers

According to the CDC, approximately 87,000 drug overdose deaths occurred in the United States from October 2023 to September 2024, and the estimated number of overdose deaths in the US attributed to fentanyl and fentanyl analogs was around 54,000 in 2024. While fentanyl and its analogs are abused via numerous administration routes, the number of seized counterfeit tablets containing these drugs is significantly high. The DEA seized over 60 million fentanyl-laced counterfeit pills in 2024, equivalent to more than 380 million lethal doses of fentanyl. Portable techniques can be especially useful for law enforcement. Raman spectroscopy, especially surface-enhanced Raman spectroscopy (SERS), is one such technique which can be useful in both field and laboratory applications due to its sensitivity and selectivity. This study demonstrates SERS for presumptive detection of fentanyl and fentanyl analogs in counterfeit tablets using two portable Raman instruments equipped with 785 nm and 1064 nm lasers, combined with commercial Ag nanoparticles and synthesized Au/Ag nanostars. The analysis of 14 counterfeit tablets revealed that SERS correctly identified fentanyl or a fentanyl analog in all samples, achieving 100 % sensitivity. However, the 1064 nm laser configuration demonstrated slightly superior performance, yielding clearer and more consistent spectral features compared to the 785 nm laser. These findings suggest that SERS, particularly with a 1064 nm laser, is a promising tool for presumptive field detection of fentanyl and its analogs in counterfeit tablets.