Impact of dopant solvents on the characterization of complex organic mixtures by atmospheric pressure photoionization source

Advances in ultra-high resolution mass spectrometry and soft ionization technologies have significantly improved the comprehension of complex organic mixtures (COMs) at the molecular level. Atmospheric pressure photoionization (APPI) is a widely used soft ionization source, but the impact of solvents on detected class distribution and double bond equivalent (DBE) range of COMs has been rarely discussed. Herein, the solvent impact of toluene (TOL), m-xylene (MX), ethylbenzene (EB), cyclohexane (CYH), decalin (DHN), and tetralin (THN) on the characterization of three different COMs were studied by APPI Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The numbers of heteroatom compounds detected in THN significantly surpassed those of heteroatom compounds in TOL. Specifically, the analysis results of three COM samples using THN detected 937, 971, and 530 more heteroatom molecules than using TOL. Moreover, the heteroatom compounds detected in THN (N 1 , N 1 O 1 , O 1 S 1 , etc.) showed a much wider DBE distribution, thereby resulting in a more comprehensive molecular profile. The finding aims to ionize more compounds and realize the analysis of non-polar aromatic compounds and heteroatomic compounds simultaneously by using APPI.