Fentanyl has killed hundreds of thousands of people globally since 2015. Detection of the drugs during interdiction is currently done through Raman spectroscopy or chemical strips—both of which require direct access to samples. Michael Malone and colleagues use a magnetic resonance technique to detect fentanyl hydrochloride inside sealed opaque containers and packages—an approach that could be used in airports, border crossings, post offices, and other contexts. Nuclear quadrupole resonance (NQR) spectroscopy sends a radio frequency pulse with a frequency corresponding to a transition energy of the target nucleus and, if the target nuclei are present, receives in return a detectable and chemically specific magnetic signature. For fentanyl, key target nuclei include the naturally abundant isotopes of nitrogen and chlorine. Effective NQR spectrometers can cost just a few thousand dollars and do not require superconducting magnets or extreme temperatures. There are some limitations: thick metallic wrapping could block detection, and the detector must be within several centimeters of the drugs. According to the authors, the technique could nevertheless help detect and divert large quantities of fentanyl.
PNAS Nexus
Standoff detection of fentanyl hydrochloride via nuclear quadrupole resonance: A multimodality pursuit
1-Jul-2025