Determination of fentanyl contamination on United States paper currency by LC-QQQ-MS.

Previous research has evaluated the extent to which cocaine and other drugs were detectable on currency in the USA. The literature was in agreement that the majority of bills exhibited some degree of contamination. With the increase of fentanyl in the illicit drug supply, this study was designed to evaluate the extent that fentanyl, cocaine, methamphetamine and other substances were present on circulating currency in 2022. A quantitative assay using liquid chromatography triple quadrupole mass spectrometry was developed and validated to detect six analytes: fentanyl, 4-anilino-N-phenethylpiperidine, acetylfentanyl, benzylfentanyl, cocaine and methamphetamine. One-dollar bills were collected from 13 cities across the country. Sample preparation consisted of soaking the bills in methanol followed by liquid-liquid extraction. Chromatographic separation was achieved using a C18 analytical column and gradient elution with ammonium formate in water (5 mM, pH 3) and 0.1% formic acid in acetonitrile. The quantitative working range for this assay was 0.1 μg to 1.0 μg per bill (equivalent to 1 ng/mL to 100 ng/mL of extract). Fentanyl was detected on the majority (63%) of samples, with 61% of samples having ≥0.1 μg of fentanyl and 4% of samples having ≥1.0 μg. Cocaine and methamphetamine were detected on 100% and 98% of bills, respectively, typically in amounts >1.0 μg. The remaining fentanyl-related substances were detected in 15% of samples in amounts no >0.69 μg per bill and exclusively in the presence of fentanyl. Unsurprisingly, areas of the country with higher incidence of fentanyl use yielded higher frequency of contaminated bills and higher concentrations. Human exposure to drugs on currency is unlikely to have any significant impacts toxicologically or pharmacologically; however, our research findings suggest that paper currency could serve as a useful substrate for surveillance of drug trends regionally, nationally and/or internationally.