Figure 3.
(a). Identification of the designer fentanyl derivative ocfentanil in an MS2C task. The top-3 candidates predicted by NPS-MS from Data Set #2 based on the spectra of ocfentanil were all structurally related to ocfentanil. The correct structure was ranked as the third-best candidate, and the top-2 candidates were its 3-fluoro (Tc = 0.64) and 4-fluoro (Tc = 0.67) isomers. In contrast, the top-3 candidates given by CFM-ID 4.0 display little resemblance to the correct structure, with Tanimoto coefficients of 0.12, 0.09, and 0.23. (b) Retrospective application of NPS-MS to identify an unknown NPS detected in a seized powder. Left, MS/MS spectra of 3-Cl-PCP predicted by CFM-ID 4.0 at 10, 20, and 40 eV. Middle, MS/MS spectra of 3-Cl-PCP predicted by NPS-MS at 10, 20, and 40 eV. Right, the top-3 compounds identified by NPS-MS and CFM-ID 4.0 in a MS2C identification task when searching the experimentally acquired 3-Cl-PCP spectra against a database of novel chemical structures anticipated by DarkNPS.