Dissolved organic matter (DOM) in petroleum refinery wastewater is an extremely complex mixture. A better understanding of chemical compositions of DOM at the molecular level is necessary for the design and optimization of wastewater treatment processes. In this study, two largely different DOM samples, one from a petroleum refinery wastewater and the other from the Suwannee river water, were characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with positive-/negative-ion electrospray ionization (ESI), and positive-ion atmospheric pressure photoionization (APPI). For wastewater DOM, a total of 6226 molecular formulae were assigned in the three ionization modes. However, only 1182 molecular formulae were common in all three mass spectra, indicating that the techniques were highly complementary in the types of molecules they ionize. Acid O_x (x = 1–9) and basic N₁O_x (x = 0–2) classes were dominant in the wastewater DOM detected in negative-ion and positive-ion ESI mode, respectively. And the wastewater DOM contains considerable amounts of polycyclic aromatic hydrocarbons that did not respond to ESI but can be ionized selectively by APPI. Compared with riverine DOM, the refinery wastewater DOM has a higher molecular complexity and is more enriched in hydrocarbon, and nitrogen- and sulfur-containing compounds. The results show that the major components of refinery wastewater DOM were distinctive from those of the natural organic matter. Though not quantitative, the results obtained by various ionization techniques were found to be complementary, and are helpful to our understanding of the selectivity of different ionization techniques as well as the molecular compositions of DOM.

中文翻译：

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电喷雾和常压光电离 FT-ICR MS 对炼油厂废水溶解有机物的电离选择性

炼油厂废水中的溶解有机物 (DOM) 是一种极其复杂的混合物。在分子水平上更好地了解 DOM 的化学成分对于废水处理工艺的设计和优化是必要的。在这项研究中，两种截然不同的 DOM 样品，一种来自炼油厂废水，另一种来自 Suwannee 河水，通过傅立叶变换离子回旋共振质谱 (FT-ICR MS) 结合正/负离子电喷雾进行表征电离 (ESI) 和正离子大气压光电离 (APPI)。对于废水 DOM，在三种电离模式下总共分配了 6226 个分子式。然而，所有三个质谱中只有 1182 个分子式是共同的，表明这些技术在它们电离的分子类型方面具有高度互补性。酸O_x (x= 1–9) 和碱性 N ₁ O _x (x= 0-2) 类别分别在负离子和正离子 ESI 模式下检测到的废水 DOM 中占主导地位。废水 DOM 中含有大量的多环芳烃，它们对 ESI 没有反应，但可以被 APPI 选择性地电离。与河流DOM相比，炼油厂废水DOM具有更高的分子复杂度，更富含烃类和含氮硫化合物。结果表明，炼油废水DOM的主要成分与天然有机物的主要成分不同。虽然不是定量的，但发现通过各种电离技术获得的结果是互补的，有助于我们了解不同电离技术的选择性以及 DOM 的分子组成。