Department of Chemistry, Biosystems Research Complex, Clemson University, Clemson, South Carolina 29634, United States.
Elemental Scientific, Inc., 7277 World Communications Dr., Omaha, Nebraska 68122, United States.
Anal Chem. 2020 Sep 15;92(18):12622-12629. doi: 10.1021/acs.analchem.0c02677. Epub 2020 Aug 28.
The spatial distributions of elemental and molecular species are vital pieces of information for a broad number of applications such as material development and bio/environmental analysis. There is currently no single analytical method that can simultaneously acquire elemental, molecular, and spatial information from a single sample. This paper presents the coupling of an NWR213 laser ablation (LA) system to the liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma for combined atomic and molecular (CAM) analysis. The work demonstrates a fundamental balance that must be considered between the extent of fragmentation of molecules and ionization of atoms for CAM analysis. Detailed studies showed that the interelectrode gap to be a critical parameter for controlling the ionization efficiency of atomic and molecular species. Utilizing Design-of-Experiment (DoE) procedures, the discharge current was also found to be a significant parameter to control. Elemental lead, caffeine, and simultaneous lead and caffeine analysis via LA-LS-APGD-MS was made possible through improved understanding of the influence of plasma parameters on the product mass spectra of laser-ablated particles. Finally, a chemical map of elemental lead and molecular caffeine, from lead nitrate and caffeine residues, was generated, demonstrating the comprehensive mapping capabilities of LA-LS-APGD-MS. The practical relevance of the capabilities is demonstrated by mapping glutamic acid from a cryosectioned chicken breast with a thallium spike deposited within the tissue. It is believed that the LA-LS-APGD-MS could be a valuable methodology for the simultaneous mapping of elemental and molecular species from a variety of samples.
元素和分子物种的空间分布对于许多应用至关重要，例如材料开发和生物/环境分析。目前没有一种单一的分析方法可以从单个样品中同时获取元素、分子和空间信息。本文介绍了将 NWR213 激光烧蚀（LA）系统与液体取样-常压辉光放电（LS-APGD）微等离子体相结合，用于原子和分子（CAM）联合分析的方法。该工作展示了在 CAM 分析中必须考虑分子碎裂程度和原子电离程度之间的基本平衡。详细研究表明，电极间隙是控制原子和分子物种电离效率的关键参数。利用实验设计（DoE）程序，还发现放电电流是控制的重要参数。通过提高对等离子体参数对激光烧蚀颗粒产物质谱影响的理解，实现了通过 LA-LS-APGD-MS 对元素铅、咖啡因以及同时分析铅和咖啡因的分析。最后，生成了来自硝酸铅和咖啡因残留物的元素铅和分子咖啡因的化学图谱，展示了 LA-LS-APGD-MS 的综合制图能力。通过在组织内沉积铊的冷冻切片鸡胸肉中对谷氨酸进行映射，证明了该方法的实际相关性。相信 LA-LS-APGD-MS 可以成为从各种样品中同时映射元素和分子物种的有价值的方法。
