Characteristic fragmentations of nitroaromatic compounds (NACs) in Orbitrap HCD and integrated strategy for recognition of NACs in environmental samples

Nitroaromatic compounds (NACs) are high of concern due to their mutagenicity, and carcinogenicity to organisms. Here, we attempted to establish a novel searching-validation-evaluation workflow that is tailored to recognize unknown NACs in environmental samples using liquid chromatography coupled with quadrupole Orbitrap high-resolution mass spectrometry (LC-Orbitrap-HRMS). We studied the fragmentation process of NAC standards in Orbitrap higher-energy collision dissociation (HCD) cells and observed that the mass loss of NO was the most prevalent among all NAC standards at both low and medium levels of collision energy. Thus, neutral loss of NO was considered as a diagnostic fragment of nitro groups and was used to screen out NACs in environmental samples. This technique is mass-loss-dependent, which enhances the recognition efficiency of NACs. Candidates exported from the PubChem compound database were further evaluated to obtain possible structures. This strategy was applied for the analysis of 24 surface soil, and we tentatively discovered two novel NACs in the analyzed samples. The semi-quantification results demonstrated that the concentrations of novel NACs were comparable to those of the ten targeted NACs in soil samples. This study provides an integrated strategy for the recognition of known and unknown NACs, which could be extended to other environmental matrices. [Display omitted] •Behavior of fragmentation of nitro-aromatic compounds (NACs) in Orbitrap MS was studied.•Specific number of nitro groups on unknown NACs is confirmable with this method.•Possible structures were evaluated based on PubChem database to reduce uncertainty.•Integrated strategy was applied in recognition of NACs in surface soil samples.•Two novel NACs in soil samples were tentatively discovered.