Premixed calibration solutions

Spectra were recorded on a Q Exactive (Orbitrap) mass spectrometer (Thermo Fisher Scientific, San Jose, CA, USA) equipped with a HESI II probe to record high resolution electrospray ionization-MS (ESI-MS). Calibration was carried out in the m/z range 74–1.822 using premixed calibration solutions (Thermo Fisher Scientific). A constant spray voltage of 4.7 kV and a dimensionless sheath gas of 5 were employed. The S-lens RF level was set to 62.0, while the capillary temperature was set to 250 °C. All samples were dissolved at a concentration range of 0.05–0.01 mg mL⁻¹ in a mixture of THF and MeOH (3 : 2) doped with 100 μmol sodium trifluoroacetate and injected with a flow of 5 μL min⁻¹.

¹H-NMR spectroscopy: 600 MHz, 128 scans, D1: 2 s. The δ-scale was referenced to the signal of residual solvent (CHD₂CN). Data were processed with MestReNova and OriginPro 9.1G. High-resolution electrospray ionization (orbitrap) mass spectrometry: The instrument (equipped with an HESI II probe) was calibrated in the m/z range 74–1822 using premixed calibration solutions (Thermo Scientific). A constant spray voltage of 4.7 kV and a dimensionless sheath gas of 5 were applied. The capillary temperature and the S-lens RF level were set to 320 °C and 62.0, respectively. The samples were dissolved with a concentration of 0.05 mg mL⁻¹ in a mixture of THF and MeOH (3:2) containing 100 mmol L⁻¹ of sodium trifluoroacetate and infused with a flow of 5 µL min⁻¹. Data were processed with XCalibur, mMass – Open Source Mass Spectrometry Tool, Microsoft Excel, OriginPro 9.1G, and custom-written algorithms (python source code).

A Q Exactive (Orbitrap) mass spectrometer (Thermo Fisher Scientific, San Jose, CA, USA) equipped with a HESI II probe was employed to record high resolution electrospray ionization–MS. Calibration was carried out in the m/z range 74–1,822 using premixed calibration solutions (Thermo Fisher Scientific). A constant spray voltage of 4.7 kV and a dimensionless sheath gas of 5 were employed. The S-lens RF level was set to 62.0, while the capillary temperature was set to 250 °C. All samples were dissolved at a concentration of 0.05 mg ml⁻¹ in a mixture of THF and MeOH (3:2) doped with 100 μmol sodium trifluoroacetate and injected with a flow of 5 μl min⁻¹.