Standoff detection of fentanyl hydrochloride via nuclear quadrupole resonance: A multimodality pursuit

Synthetic opioids, chiefly fentanyl, are responsible for nearly 70% of global annual drug deaths due to their extreme toxicity, ease of manufacture, and addictiveness. We show the magnetic resonance technique of nuclear quadrupole resonance (NQR) spectroscopy can be used for the standoff detection of fentanyl hydrochloride (HCl), likely the most common illicit synthetic opioid, even through opaque packaging such as cardboard, plastic, and glass. Combining work in synthesis, crystallography, density functional theory, and nuclear magnetic resonance, we report the electric field gradient tensor parameters of the ${\mathrm{ }}^{14}$ N and ${\mathrm{ }}^{35}$ Cl nuclei in fentanyl HCl to determine the chemically specific NQR frequencies. We directly observe the NQR signal for the aniline nitrogen and measure the associated relaxation times. The results show a robust ability for the standoff detection of relevant quantities of fentanyl HCl, at room temperature, with an inexpensive system.