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Rapid fingerprinting of lignin by ambient ionization high resolution mass spectrometry and simplified data mining
Analytica Chimica Acta ( IF 6.2 ) Pub Date : 2017-11-01 , DOI: 10.1016/j.aca.2017.09.012
Elizabeth A. Crawford , Stefanie Gerbig , Bernhard Spengler , Dietrich A. Volmer

Ambient ionization techniques are typically used to analyze samples in their native states with minimal or no sample pretreatment prior to mass spectrometric (MS) analysis. Desorption electrospray ionization (DESI) and direct analysis in real time (DART) were systematically investigated in this work for direct solid analysis of depolymerized lignin samples, with the goal of rapidly fingerprinting these samples, to efficiently characterize the subunits of this renewable energy source. High resolution MS was required for enhanced selectivity in this study due to the inherent structural complexity of lignin. DESI provided results across a broader mass range (up to m/z 700) than DART and also ionized saturated compounds of low oxygen-to-carbon (O/C) ratios and low double bond equivalents (DBE). While DART detected the same core lignin monomeric and dimeric compounds as seen with DESI and electrospray ionization (ESI), results were restricted to a narrower mass range to m/z 500, due to thermal degradation and losses of methoxy groups. In contrast to DESI and ESI, the DART spectra were nearly void of saturated components. On a structural level, the core lignin compounds were visually fingerprinted and ionization method performances critically assessed by employing simplified Kendrick-based data mining approaches. A novel simplified data visualization approach was developed in this work based on modified Kendrick mass defect (KMD) filtering for lignin subunits and plotting the mass defect values against the degree of unsaturation. Direct visualization of monomeric, dimeric and trimeric lignin species was simplified by the KMD separation plots, easily allowing the core lignin compounds to be visually identified and compared. Modified KMD bases, namely methoxy and phenol bases, which represent monomer-specific lignin constituents, were successfully used to classify and group the complex mixture of lignin species. Further separation of methoxy-related lignin species was successfully achieved by employing the more specific phenolic KMD base.

中文翻译:

通过环境电离高分辨率质谱和简化数据挖掘对木质素进行快速指纹识别

在质谱 (MS) 分析之前,环境电离技术通常用于分析处于天然状态的样品,只需最少或不进行样品预处理。在这项工作中系统地研究了解吸电喷雾电离 (DESI) 和直接实时分析 (DART),用于解聚木质素样品的直接固体分析,目的是快速对这些样品进行指纹识别,以有效表征这种可再生能源的亚基。由于木质素固有的结构复杂性,本研究中需要使用高分辨率 MS 来提高选择性。DESI 提供了比 DART 更宽的质量范围(高达 m/z 700)的结果,并且还离子化了低氧碳 (O/C) 比和低双键当量 (DBE) 的饱和化合物。虽然 DART 检测到与 DESI 和电喷雾电离 (ESI) 相同的核心木质素单体和二聚体化合物,但由于热降解和甲氧基丢失,结果仅限于 m/z 500 的较窄质量范围。与 DESI 和 ESI 相比,DART 光谱几乎没有饱和成分。在结构层面上,核心木质素化合物进行了视觉指纹识别,并通过采用基于 Kendrick 的简化数据挖掘方法严格评估了电离方法的性能。在这项工作中开发了一种新颖的简化数据可视化方法,该方法基于对木质素亚基的改进 Kendrick 质量缺陷 (KMD) 过滤,并根据不饱和度绘制质量缺陷值。单体的直接可视化,KMD 分离图简化了二聚体和三聚体木质素种类,可以轻松地对核心木质素化合物进行视觉识别和比较。修饰的 KMD 碱基,即代表单体特定木质素成分的甲氧基和苯酚碱基,成功地用于对木质素种类的复杂混合物进行分类和分组。通过使用更具体的酚类 KMD 碱,成功实现了甲氧基相关木质素种类的进一步分离。
更新日期:2017-11-01
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