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This study explores the experimental conditions for direct Atmospheric Pressure Photoionization (APPI) in mass spectrometry (MS) analysis of polycyclic aromatic hydrocarbons (PAHs). Solutions were injected at a flow rate of 40 µL/min using a Harvard syringe pump, with the APPI source maintained at 400°C. Key parameters included specific gas flow rates and temperatures, facilitating effective ionization. The research also presents a proposed electron transfer mechanism involving toluene solvent, coupled with a quantum mechanical analysis of reaction transition states, enhancing understanding of PAH ionization.
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Experimental conditions for MS Analysis For direct APPI, each of the solutions was injected into the APPI source at a flow rate of 40 µL/min using a Harvard (Holliston, MA, USA) Model 11 syringe pump. The APPI source temperature was held at 400°C. Other operating mass spectrometric parameters were as follows: 10, 5, and 0 arbitrary units for the sheath, auxiliary, and sweep gas flow rates, respectively; 300°C for the capillary temperature; 15 V for the capillary voltage; and 70 V for the tube lens. Boil-off from liquid nitrogen was used as both the sheath and auxiliary gases for the ionization source.
Figure 1S. The proposed electron transfer coupled hydrogen transfer reaction mechanism for to generate protonated PAH ions with toluene solvent in the previous study.1 (S: solvent, M: PAH analyte)
Figure 2S. Pictorial description of simulated configuration of transition states described in Figure 3a. TS (Ortho H) TS (Methyl H) TS (Meta H) TS (Para H)
Figure 2S. Pictorial description of simulated configuration of transition states described in Figure 3b. TS (Methyl H) TS (Ortho H) TS (Meta H) TS (Para H)
Figure 3S. Relative energy diagram calculated by quantum mechanical calculation for the reactions between acridine and solvent molecular ions. C13H9N + S•+ C13H9N •++ S H+(C13H9N) + (S-H)• S= Solvent
