High-Field FTICR-MS Data Evaluation of Natural Organic Matter: Are CHON5S2 Molecular Class Formulas Assigned to 13C Isotopic m/z and in Reality CHO Compo

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• 作者：Peter Herzsprung ; Wolf v. T眉mpling ; Norbert Hertkorn ; Mourad Harir ; Kurt Friese ; Philippe Schmitt-Kopplin
• 刊名：Analytical Chemistry
• 出版年：2015
• 出版时间：October 6, 2015
• 年：2015
• 卷：87
• 期：19
• 页码：9563-9566
• 全文大小：231K
• ISSN：1520-6882

文摘

The analysis of dissolved organic matter (DOM) using high-field Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) poses challenges in molecular formula assignment. The consideration of ¹³C isotopes provides new insights into the consistent elemental formula solutions. Modern software helps to overcome misinterpretation, but false assignments of molecular classes to mass peaks have rarely been elucidated until now. It will be demonstrated that this can be important with formula assignments comprising exactly five nitrogen and two sulfur atoms in DOM data sets: the molecular class CHON₅S₂. The existence of such components in DOM under tripeptide Met鈥揌is鈥揅ys formed with the formula C₁₄H₂₃O₄N₅S₂ cannot be excluded; however, components containing 5 N and 2 S should be suspected to not be highly abundant. The true elemental compositions of such unusual 鈥淣₅S₂ moieties鈥?were calculated using Suwannee River fulvic acid (SRFA) data from the literature and one data set from acidic pit lake pore water. The replacement of a H₃N₅S₂ moiety with a ¹³C₁¹²C₅O₄ moiety explained more than 95% of the questionable 鈥淣₅S₂ moieties鈥? This finding was proved by calculation of 未¹³C鈥?values from relative peak intensities.