Purcell Jeremiah M, Rodgers Ryan P, Hendrickson Christopher L, Marshall Alan G
National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310-4005, USA.
J Am Soc Mass Spectrom. 2007 Jul;18(7):1265-73. doi: 10.1016/j.jasms.2007.03.030. Epub 2007 Apr 10.
We determine the elemental compositions of aromatic nitrogen model compounds as well as a petroleum sample by atmospheric pressure photoionization (APPI) and electrospray Ionization (ESI) with a 9.4 Tesla Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. From the double-bond equivalents calculated for the nitrogen-containing ions from a petroleum sample, we can infer the aromatic core structure (pyridinic versus pyrrolic nitrogen heterocycle) based on the presence of M(+.) (odd-electron) versus M+H (even-electron) ions. Specifically, nitrogen speciation can be determined from either a single positive-ion APPI spectrum or two ESI (positive- and negative-ion) spectra. APPI operates at comparatively higher temperature than ESI and also produces radical cations that may fragment before detection. However, APPI fragmentation of aromatics can be eliminated by judicious choice of instrumental parameters.
我们使用一台9.4特斯拉傅里叶变换离子回旋共振（FT-ICR）质谱仪，通过大气压光电离（APPI）和电喷雾电离（ESI）来测定芳香族含氮模型化合物以及一个石油样品的元素组成。根据从石油样品中含氮离子计算出的双键当量，我们可以基于M(+.)（奇电子）离子与M+H（偶电子）离子的存在情况，推断出芳香核结构（吡啶型与吡咯型氮杂环）。具体而言，氮形态可以从单个正离子APPI光谱或两个ESI（正离子和负离子）光谱中确定。APPI在比ESI相对更高的温度下运行，并且还会产生在检测前可能发生碎裂的自由基阳离子。然而，通过明智地选择仪器参数，可以消除芳香族化合物的APPI碎裂。
