It has long been a challenging task to achieve both chemical resolution and mass completeness for the analysis of atmospheric organic compounds. This study presents a data analysis workflow for nontarget tandem high-resolution mass spectrometry, aiming at the full speciation of functionalized organic compounds in complex atmospheric samples without unambiguous molecular structure assignment. The workflow was demonstrated for the measurements of four types of atmospherically-relevant samples, including primary-emission aerosols, secondary organic aerosols, size-resolved ambient aerosols and rainwater, using an ultrahigh-performance liquid chromatography electrospray ionization quadrupole Orbitrap high-resolution mass spectrometry (UHPLC/ESI Q-Orbitrap), but could be applicable to other environmental samples. The combined MS¹ and MS² data provided molecular formula, functional group and more accurate aromaticity information for 68.1-88.8% of deprotonated molecules and 58.6-84.7% of protonated molecules in a single mass spectrometry run. We determined relative abundances of 22 and 21 compound categories for deprotonated and protonated molecules, respectively, on the basis of the assignment of a variety of oxygen-, nitrogen- and sulfur- containing functional groups. The molar concentrations of the compound categories were further semi-quantified using surrogate standards in ESI negative mode. The molar concentration of individual compound category ranged from 10^-4 to 1 nmol µg^-1 source aerosol mass, 3×10^-3 to 2 nmol m^-3 in the atmosphere and 2×10^-3 to 1 nmol mL^-1 rainwater. The assignment and quantification of functional groups provided new chemical fingerprints of complex organic compounds across the samples, which not only help one to trace the sources, formation and aging of organic compounds in the atmosphere, but also allow the use of group contribution methods to study physicochemical properties of organic aerosols.
 

有机颗粒物,高分辨质谱,非靶向