Stability-indicating reversed-phase HPLC method development and characterization of impurities in vortioxetine utilizing LC–MS, IR and NMR

One part of routes of producing impurities of vortioxetine and their relationship. In route 1, SMA may contain p-bromoiodobenzene (SMA-1) as an impurity, and affords Imp-A following the same reaction that gives vortioxetine. Simultaneously, SMA-1 affords Imp-C in the subsequent reaction of vortioxetine when no reaction with SMB occurs. In route 2, vortioxetine might be oxidized at high temperatures, affording sulfoxide Imp-B. In route 3, SMB might contain 2,6-dimethylbenzenethiol (SMB-1) as an impurity, affording Imp-E by the same reaction that yields vortioxetine. In route 4, SMA affords Imp-F via Imp-D when no reaction with SMB occurs. [Display omitted] •Imp-A, a new compound, was found and identified by NMR, MS, and IR analyses.•Identification and characterization of process-related impurities.•The pathway for the formation of the impurities has been discussed.•A RP-HPLC method is developed for quantitatively determining impurities. The current study reports the development and validation of a stability-indicating reversed phase HPLC method for the separation and identification of potential impurities in vortioxetine, a recently developed antidepressant. The structures of a new compound and four process-related impurities formed during the synthesis were characterized and confirmed by NMR, MS, and IR spectroscopy analyses. The most probable formation mechanisms of the impurities identified were proposed. Based on the characterization data, the new compound was proposed to be 1-[4-[(2,4-dimethylphenyl)thio]phenyl]-piperazine. In addition, an efficient chromatographic method was optimized to separate and quantify the impurities, which were obtained in the 0.05–0.75μg/mL range. The developed HPLC method was validated with respect to accuracy, precision, linearity, robustness, and limits of detection and quantitation.