Square-wave adsorptive stripping voltammetry (SWAdSV) is proposed as a fast, simple, and sensitive approach toward the detection, identification, and semi-quantitation of fentanyl in seized drug samples using screen-printed carbon electrodes. Electrochemical oxidation of fentanyl resulted in the formation of two anodic peaks, one at 0.75 V (peak I) and the second at 0.88 V (peak II) versus a Ag/AgCl pseudo reference electrode. Voltammetric measurements were conducted under optimized experimental conditions using fentanyl standards ranging from 0.076 μg/mL to 6.9 μg/mL, which resulted in a limit of detection of 0.037 μg/mL. Reproducibility was assessed as the average percent relative standard deviation of the slopes of calibration curves and was 2.6% for oxidation peak I and 7.4% for oxidation peak II in cell. Detection capabilities were assessed in a 5-mL cell and in a 100 microliter drop. Interference studies were conducted with cocaine, methamphetamine, quinine, caffeine, and acetaminophen. The mechanism for the electrochemical oxidation of fentanyl to norfentanyl is also described. Accuracy and suitability of the method for seized drug analysis was assessed using 11 simulated samples. Suitability of the method for future analysis of fentanyl in oral fluid was assessed.
