Detection of para, ortho, meta-fluorofentanyl by surface-enhanced raman spectroscopy

The illegal use of fentanyl and fentanyl analogs is increasing day by day, and this leads to more overdose deaths. Fentanyl is 100 times more effective than morphine, while some fentanyl analogues are more potent than fentanyl. Isomers of the molecules can also have different potencies. Therefore, detecting and differentiating fentanyl analogs is critical in cases of a possible overdose. There are several methods to detect fentanyl and fentanyl analogs but confirmatory techniques such as Gas Chromatography-Mass Spectroscopy (GC-MS) or Liquid Chromatography-Mass Spectroscopy (LC-MS) is not sufficient to differentiate isomers. However, Surface-enhanced Raman spectroscopy (SERS) is a successful method for detecting isomers thanks to its capability of yielding spectroscopic fingerprints of the analytes. In this study, various SERS methods were compared in order to distinguish para fluorofentanyl, which is one of the most common fentanyl analogs in illicit mixtures, and its isomers ortho fluorofentanyl and meta fluorofentanyl. First, Density Functional Theory (DFT) calculations were done to examine whether these analogs have different spectra in theory. The spectra obtained from the theoretical calculations were compared with the spectra obtained from the Normal Raman and SERS experiments. Bimetallic gold/silver nanostars (Au/Ag NS) were synthesized for the applied SERS protocols. Inorganıic salts magnesium chloride and potassium bromide were used in the compared protocols for the aggregation of nanostars. The protocol in which potassium bromide was used gave a better enhancement so it was used to calculate the limit of detection (LOD) and limit of detection (LOQ). The obtained results show that SERS is a successful technique to detect isomers of fentanyl analogs.