Carbonyl compounds are important components of natural organic matter (NOM) with high reactivity, so that play a pivotal role in the dynamic transformation of NOM. However, due to the lack of effective analytical methods, our understanding on the molecular composition of these carbonyl compounds is still limited. Here, we developed a high-throughput screening method to detect carbonyl molecules in complex NOM samples by combining chemical derivatization with electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR-MS). In six different types of dissolved organic matter (DOM) samples tested in this study, 20–30 % of detected molecules contained at least one carbonyl group, with relative abundance accounted for 45–70 %. These carbonyl molecules displayed lower unsaturation level, lower molecular weight, and higher oxidation degree compared to non-carbonyl molecules. More importantly, the measured abundances of carbonyl molecules were consistent with the results of C nuclear magnetic resonance (NMR) analysis. Based on this method, we found that carbonyl molecules can be produced at DOM-ferrihydrite interface, thus playing a role in shaping the molecular diversity of DOM. This method has broad application prospects in screening carbonyl compounds from complex mixtures, and the same strategy can be used to directional identification of molecules with other functional groups as well.

中文翻译：

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定向衍生结合超高分辨率质谱高通量鉴定天然有机物中的羰基化合物

羰基化合物是天然有机物（NOM）的重要组成部分，具有高反应活性，在NOM的动态转化中发挥着关键作用。然而，由于缺乏有效的分析方法，我们对这些羰基化合物的分子组成的了解仍然有限。在这里，我们开发了一种高通量筛选方法，通过将化学衍生化与电喷雾电离傅里叶变换离子回旋共振质谱（ESI FT-ICR-MS）相结合来检测复杂NOM样品中的羰基分子。在本研究测试的六种不同类型的溶解有机物（DOM）样品中，20%~30%的检测分子含有至少一个羰基，相对丰度占45%~70%。与非羰基分子相比，这些羰基分子表现出较低的不饱和度、较低的分子量和较高的氧化度。更重要的是，测量的羰基分子丰度与13C核磁共振（NMR）分析结果一致。基于该方法，我们发现在DOM-水铁矿界面处可以产生羰基分子，从而在塑造DOM分子多样性方面发挥作用。该方法在复杂混合物中筛选羰基化合物方面具有广阔的应用前景，同样的策略也可用于定向鉴定具有其他官能团的分子。