Abstract
The opioid overdose crisis in North America worsened during the COVID-19 pandemic, with multiple jurisdictions reporting more deaths per day due to the fentanyl-contaminated drug supply than COVID-19. The rapid quantitative detection of fentanyl in the illicit opioid drug supply or in bodily fluids at biologically relevant concentrations (i.e., <80 nM) remains a significant challenge. Electroanalytical techniques are inexpensive and can be used to rapidly detect fentanyl, but detection limits need to be improved. Herein, we detail the development of an electrochemical-based fentanyl analytical detection strategy that used a glassy carbon electrode modified with electrochemically reduced graphene oxide (ERGO) via electrophoretic deposition. The resulting surface was further electrochemically reduced in the presence of fentanyl to enhance the sensitivity. Multiple ERGO thicknesses were prepared in order to prove the versatility and ability to fine-tune the layer to the desired response. Fentanyl was detected at <10 ppb (<30 nM) with a limit of detection of 2 ppb and a calibration curve that covered 4 orders of concentration (from 1 ppb to 10 ppm). This method was sensitive to fentanyl analogues such as carfentanil. Interference from the presence of 100-fold excess of other opioids (heroin, cocaine) or substances typically found in illicit drug samples (e.g. caffeine and sucrose) was not significant.