Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
J Am Soc Mass Spectrom. 2017 Jun;28(6):1036-1047. doi: 10.1007/s13361-016-1550-6. Epub 2016 Dec 19.
A liquid sampling-atmospheric pressure afterglow microplasma ionization (LS-APAG) source is presented for the first time, which is embedded with both electrospray ionization (ESI) and atmospheric pressure afterglow microplasma ionization (APAG) techniques. This ion source is capable of analyzing compounds with diverse molecule weights and polarities. An unseparated mixture sample was detected as a proof-of-concept, giving complementary information (both polarities and non-polarities) with the two ionization modes. It should also be noted that molecular mass can be quickly identified by ESI with clean and simple spectra, while the structure can be directly studied using APAG with in-source oxidation. The ionization/oxidation mechanism and applications of the LS-APAG source have been further explored in the analysis of nonpolar alkanes and unsaturated fatty acids/esters. A unique [M + O - 3H] was observed in the case of individual alkanes (C-C) and complex hydrocarbons mixture under optimized conditions. Moreover, branched alkanes generated significant in-source fragments, which could be further applied to the discrimination of isomeric alkanes. The technique also facilitates facile determination of double bond positions in unsaturated fatty acids/esters due to diagnostic fragments (the acid/ester-containing aldehyde and acid oxidation products) generated by on-line ozonolysis in APAG mode. Finally, some examples of in situ APAG analysis by gas sampling and surface sampling were given as well. Graphical Abstract ᅟ.
首次提出了一种液相采样-常压辉光微等离子体电离（LS-APAG）源，该源同时嵌入了电喷雾电离（ESI）和常压辉光微等离子体电离（APAG）技术。该离子源能够分析具有不同分子量和极性的化合物。作为概念验证，检测了未分离的混合物样品，两种电离模式提供了互补的信息（包括极性和非极性信息）。还应该注意的是，ESI 可以快速识别分子量，得到干净、简单的谱图，而 APAG 则可以在源内氧化直接研究结构。进一步探索了 LS-APAG 源的电离/氧化机制及其在非极性烷烃和不饱和脂肪酸/酯分析中的应用。在优化条件下，对于单个烷烃（C-C）和复杂碳氢化合物混合物，可以观察到独特的[M+O-3H]。此外，支链烷烃产生了显著的源内碎片，可进一步应用于烷烃异构体的鉴别。该技术还由于在 APAG 模式下在线臭氧解产生的诊断碎片（含酸/酯的醛和酸氧化产物），可以方便地确定不饱和脂肪酸/酯中的双键位置。最后，还给出了一些通过气体采样和表面采样进行原位 APAG 分析的示例。
