C18 precolumn guard

The LC–MS analysis was performed with the use of an Agilent 6520 series high-resolution Q-TOF system and a UHPLC 1290 series system (Agilent Technologies, Santa Clara, CA, USA) with a Kinetex C18 (2.1 × 50 mm, dp = 1.7 μm) column and a C18 precolumn guard (Phenomenex, Torrance, USA). In order to perform both qualitative and quantitative analysis of the studied processes, the MS detector was operated in the positive mode in the extended dynamic range (2 GHz). MassHunter workstation software version B.04.00 was used for the control of the system, data acquisition, qualitative and quantitative analysis. To ensure accuracy in mass measurements, a reference mass correction was applied and masses 121.050873 and 922.009798 were used as lock masses. MS detection based on the extracted ion current chromatograms (EIC) was applied for the quantitative analysis of dapoxetine and its metabolites; next, the automatic MS/MS mode (using the abundance algorithm) was used to register their fragmentation spectra. All the chromatographic and spectrometric parameters are described in Table S1.

The LC-HR-MS analysis was performed with the use of Agilent high-resolution Q-TOF system series 6520 and UHPLC system series 1290 (Agilent Technologies, Santa Clara, CA, USA) with Kinetex C18 (2.1 × 50 mm, dp = 1.7 μm) column and C18 precolumn guard (Phenomenex, Torrance, CA, USA). In order to perform both qualitative and quantitative analysis of the studied processes, the MS detector was tuned in a positive mode in extended dynamic range (2 GHz). MassHunter workstation software in version B.04.00 (Agilent Technologies, Santa Clara, CA, USA) was used for the control of the system, data acquisition, qualitative, and quantitative analysis. To ensure accuracy of the masses’ measurements, a reference mass correction was applied and masses 121.050873 and 922.009798 were used as lock masses. MS detection based on the extracted ion current chromatograms (EIC) was applied for the quantitative analysis of nebivolol, and then auto MS/MS mode (using abundance algorithm) was used for registration of their fragmentation spectra. All the chromatographic and spectrometric parameters are described in Table S1.

The conditions for performing chromatography were optimized based on previous studies. The LC–MS analysis was conducted using an Agilent high-resolution Q-TOF system series 6520 equipped with an electrospray ionization source (ESI) and UHPLC system series 1290. For the analysis, a Kinetex-C18 (2.1 mm × 50 mm, dp = 1.7 μm) reversed-phase chromatographic column with a C18 precolumn guard (Phenomenex, Torrance, CA, USA) was employed. The MassHunter workstation software version B.06.00 (Agilent Technologies, Santa Clara, CA, USA) was used to control of the UHPLC-HRMS system, manage data acquisition, and perform qualitative and quantitative analysis. To ensure accuracy in mass measurements, a reference mass correction was implemented by utilizing lock masses of 121.050873 and 922.009798 (API-TOF Reference Mass Solution Kit; Agilent Technologies, Santa Clara, CA, USA). The process of optimizing instrument conditions commenced with the tunning of the MS detector in a positive mode operating within an extended dynamic range (2 GHz). Detailed information regarding the chromatographic and spectrometric parameters can be found in Table S1.