Trace level detection of select opioids (fentanyl, hydrocodone, oxycodone, and tramadol) in suspect pharmaceutical tablets using surface-enhanced Raman scattering (SERS) with handheld devices.

The opioid crisis in the USA has resulted in over 702,000 overdose fatalities between 1999 and 2017 and can be attributed to over-prescription of opioids and abuse of synthetic opioids in combination with other illicit drugs. A rapid and sensitive SERS method has been developed for trace detection of opioids including fentanyl, hydrocodone, oxycodone, and tramadol in low-dosage suspect tablets using two different handheld Raman spectrometers equipped with 785 and 1064 nm lasers. The method involves a micro-extraction procedure using 10% methanol in deionized water, followed by filtration and addition of colloidal silver and aqueous KBr, resulting in a mixture that can be measured directly via a glass vial. The lowest concentration (Cmin ) of fentanyl, tramadol, oxycodone, and hydrocodone standards that yielded a positive match was 250 ng/ml, 5, 10, and 10 μg/ml using the 1064 nm laser device and 100 ng/ml, 1 μg/ml, 500 ng/ml, and 750 ng/ml using the 785 nm laser device, respectively. For the analysis of suspect tablets containing these opioids, the Cmin ranges between 5 and 75 µg/ml for 1064 nm laser device and 1 and 50 µg/ml for 785 nm laser device. The overall positive identification rate for all the opioids studied in the suspect counterfeit tablets analyzed ranged from 80% to 100%. The use of SERS for rapid chemical identification at remote sampling sites, such as international mail facilities (IMFs) and express courier hubs (ECHs), provides a rugged, simple, and practical method applicable for point-of-entry sampling and analysis.