Sun Jingjing, Liang Ying, Fu Qing-Long
Hubei Key Laboratory of Yangtze River Basin Environmental Aquatic Science, School of Environmental Studies, China University of Geosciences, Wuhan 430078, China.
J Am Soc Mass Spectrom. 2023 Aug 2;34(8):1813-1820. doi: 10.1021/jasms.3c00208. Epub 2023 Jul 11.
The interpretation of data and optimization spectral acquisition of dissolved organic matter (DOM) by ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) have been challenging due to the varied instrument performances among laboratories and the complex chemical characteristics of DOM. However, a universal spectral optimization strategy for FT-ICR MS spectra is still unavailable. The results of this study showed that the number, intensity, and resolving power of all assigned peaks increased with the ion accumulation time (IAT) and DOM concentrations within a reasonable range. The space-charge effect induced by the excess ions in the ICR cell can deteriorate the data quality of the FT-ICR MS spectra, which could be inspected by examining the mass errors and intensity deviation of the monoisotopic and C-isotopic peaks based on the C-isotopic pattern. The maximum absolute mass error and C-isotopic pattern-based intensity deviation are two critical criteria for inspecting the space-charge effect, which was suggested to be 2.0 ppm and 20%, respectively. Therefore, a novel strategy based on the C-isotopic pattern has been proposed in this study to optimize the FT-ICR MS spectra of DOM based on their wide occurrence of monoisotopic and C-isotopic signals. This optimization strategy has laid the fundamentals for the method development of FT-ICR MS and could be extended to different FT-ICR MS instruments and various organic complex mixtures.
由于各实验室仪器性能不同以及溶解有机物（DOM）复杂的化学特性，通过超高分辨率傅里叶变换离子回旋共振质谱（FT-ICR MS）对DOM进行数据解读和光谱采集优化一直具有挑战性。然而，目前仍没有适用于FT-ICR MS光谱的通用光谱优化策略。本研究结果表明，在合理范围内，所有已归属峰的数量、强度和分辨率随离子累积时间（IAT）和DOM浓度的增加而增加。ICR池中过量离子引起的空间电荷效应会降低FT-ICR MS光谱的数据质量，这可以通过基于碳同位素模式检查单同位素峰和碳同位素峰的质量误差和强度偏差来检测。最大绝对质量误差和基于碳同位素模式的强度偏差是检测空间电荷效应的两个关键标准，建议分别为2.0 ppm和20%。因此，本研究基于碳同位素模式提出了一种新策略，以优化DOM的FT-ICR MS光谱，因为其广泛存在单同位素和碳同位素信号。这种优化策略为FT-ICR MS方法的发展奠定了基础，并可扩展到不同的FT-ICR MS仪器和各种有机复杂混合物。
