Fusion 100t

A 2 μL stock solution (10 mg/mL) was loaded using a disposable glass Pasteur pipette (Volac; Poulten & Graf Ltd., Barking, UK) onto the center of a chromatographic paper tip (Whatman 1 Chr., Kent, UK). The positive-ion mode of the Q-Exactive orbitrap MS (Thermo Fisher Scientific, Inc., Rockford, IL, USA) was used to collect the data over the range of m/z 50–600. To make a sharp tip, the chromatographic paper was cut into dimensions of 6 mm base and 14 mm height. A syringe pump (Fusion 100T; Chemyx, Stafford, TX, USA) was used to load the ethanol solvent onto the sample-loaded paper at a flow rate of 15 μL/min. A spray voltage of 4.5 kV was directly applied to the paper tip for the ionization of the sample. The other parameters for the PSI experiment were as follows: capillary temperature 300, S-lens RF level 50, mass resolution 140,000 (full-width at half-maximum), and maximum injection time 150 ms. The automatic gain control was set to 1 × 10⁶.
To perform the MS/MS experiments, three different stepped normalized collision energies (10, 30, and 50) were used with the same instrument. The instrument was operated in the positive-ion mode. The other operative parameters for the MS/MS experiments were as follows: sheath and auxiliary gas flow rate 10 and 0 (arbitrary units), respectively; spray voltage 3.60 kV; capillary temperature 300; and S-lens RF level 50.

A Q-Exactive™ Quadrupole-Orbitrap™ mass spectrometer (Thermo Fisher Scientific Inc., Rockford, IL, USA) was used to perform PSI experiments. Methanol was purchased from Sigma-Aldrich (St. Louis, MO, USA) and used without further purification. NNFE was dissolved in methanol at a concentration of 50 μg/mL to prepare a stock solution. Then, the stock solution was diluted to a concentration of 10 μg/mL . Two microliters of the prepared solution was loaded onto a paper tip to perform the PSI experiment. (+) Mode PSI was used over a range of m/z 100–2000. Normal chromatographic paper was used in the PSI experiment. A disposable glass Pasteur pipette (Volac, Poulten & Graf Ltd, UK) was used to load the extracted sample directly onto the centre of the chromatographic paper tip. To make a sharp tip, the chromatographic paper was cut at dimensions of 6-mm base and 14-mm height. A syringe pump (Fusion 100 T, Chemyx, Stafford, TX, USA) was used to load the methanol solvent onto the sample-loaded paper. The flow rate was 40 μL/min, and the voltage directly applied on the paper for ionisation was 3–7 kV. Other parameters for PSI were as follows: spray voltage, 4.5 Kv; capillary temperature, 300 °C; mass resolution 140,000 (FWHM); maximum injection (IT) time, 150 ms; and automatic gain control (AGC), 1 E⁶.