Xueyan Yang,Siman Ren,Yuwei Wang,Gan Yang,Yueyang Li,Chuang Li,Lihong Wang,Lei Yao,Lin Wang
Evaluating the volatility of organic compounds based solely on their molecular formulas would avoid tough demands in deriving molecular structures. Here, we deployed an iodide-adduct Long Time-of-Flight Chemical Ionization Mass Spectrometry (LToF-CIMS) combined with a Filter Inlet for Gases and AEROsols (FIGAERO) to investigate molecular formulas and thermograms of organic compounds on ambient particulate samples collected in the summer of 2021 in a suburban site of Shanghai and to estimate saturation vapor pressures of low- and semivolatile components of ambient organic aerosols. Then, a hierarchical cluster analysis and a subsequent classification of obtained clusters by similarity calculation were applied to the measured data set of molecular formulas and saturation vapor pressures of organic aerosols with at least a 2/3 appearance frequency, together with a similar data set collected at a rural site in the Beijing–Tianjin–Hebei region during the winter of 2018 (Ren et al., 2018), to classify all compounds into multiple groups. For each group of compounds, parametrizations between volatility and elemental composition were derived, and then relationships between each group of parameters and the mean O:C were established to achieve a volatility-molecular formula parametrization with the O:C as a key input. Statistical comparison of estimated volatilities of low-volatile organic compounds shows a much better performance of our parametrization than previous molecular formula-based ones.
Lulu He,Jianqin Qian,Peixi Zhu,Weifeng Yang,Yuanbin She
A simple and sensitive method was developed for separation and characterization of seventeen impurities from commercial latamoxef sodium for injection by liquid chromatography combined with electrospray ionization and QTOF mass spectrometer (LC-ESI-QTOF MS). The chromatographic separation was performed on a Boston Green ODS-AQ C18 column (250 mm × 4.6 mm, 5 μm) under gradient mode using binary mobile phase: (A) ammonium acetate (10 mM)-methanol (99:1, v/v) and (B) ammonium acetate (10 mM)-methanol (70:30, v/v). Based on tandem multistage MS and high resolution MS data, the molecular formulas and structures of unknown impurities were inferred. A plausible formation mechanism of impurities was also proposed. In addition, the fragmentation regularity of degraded impurities in positive-ion mode was summarized.
The certain challenge for the utilization of bio-oil is to investigate the nature and formation of reactive large molecular (heavy) components (>200 Da) in bio-oil. In order to investigate the chemical composition of the heavy components in the bio-oils from the pyrolysis of cellulose , hemicellulose and lignin, the molecular formulas of the heavy compounds and the large aromatic structures were obtained based on the results from the Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) and the ultraviolet fluorescence (UV-F) spectrometer. The results indicated that both the oxygen content and yield of the heavy components showed the highest in the cellulose-oil and the lowest in the lignin-oil. The large molecular compounds were formed mainly via the recombination of the O-containing species, which could be changed at different temperatures and heating rates. Large amount of heavy saccharide and phenolic species existed in cellulose-oil and hemicellulose-oil, while almost no saccharide species and little phenolic species were detected in the lignin-oil. The main heavy components in the lignin-oil were lipids rather than the phenolic species. The heavy components in the bio-oil from the biomass should be mainly derived from the pyrolysis of the cellulose individually or the interactions among the three components.
危险品化学品经营许可证（带存储）