Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo Nám. 542/2, 166 10, Prague 6, Czech Republic.
Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo Nám. 542/2, 166 10, Prague 6, Czech Republic.
Talanta. 2021 Jun 1;228:122212. doi: 10.1016/j.talanta.2021.122212. Epub 2021 Feb 12.
Robust decoupling of the ESI potential from the separation potential in CE-ESI-MS interfaces is very important for the high performance of the CE-ESI-MS devices and their applications for highly sensitive analyses of ionogenic compounds. In this study, we utilize a nanoflow sheath-liquid CE-ESI-MS interface composed of a quartz emitter and a separation fused silica capillary treated by etching, which are threaded to cross coupling for sheath liquid and electrode connection. Specifically, we have tested the ability of the interface to decouple the ESI potential from the separation potential at different positions of the separation capillary and ESI emitter tube tips. The interface with the separation capillary tip protruding the emitter tip by 20 μm did not provide sufficient robustness. The real ESI potential (delivered as 2.0 kV from the independent high voltage power supply HV2) ranged from 2.1 kV to 4.5 kV depending on the applied separation voltage (12.0-20.0 kV, provided by the power supply HV1) and electric conductivity of the background electrolyte (BGE) used. The interface robustness was partially improved when the capillary tip was aligned with the emitter tip. However, the complete decoupling of the spray and separation potentials was achieved only when the capillary tip was retracted 20 μm inside the emitter. In this arrangement, the ESI potential was stable and independent of both the separation potential (voltage) and the BGE conductivity. Moreover, this setting provided better sensitivity for the CE-ESI-MS analysis of selected drugs and benzylpyridinium cations than the setup with the capillary tip aligned with or protruding the emitter tip.
在 CE-ESI-MS 接口中，将 ESI 势能与分离势能有效解耦对于提高 CE-ESI-MS 仪器的性能及其在对离子型化合物进行高灵敏度分析方面的应用非常重要。在本研究中，我们利用由石英喷咀和经蚀刻处理的分离熔融石英毛细管组成的纳流鞘液 CE-ESI-MS 接口，该接口通过交叉耦合来进行鞘液和电极连接。具体而言，我们已经测试了该接口在分离毛细管和 ESI 喷咀管尖端的不同位置将 ESI 势能与分离势能解耦的能力。当分离毛细管尖端突出喷咀尖端 20μm 时，该接口没有提供足够的稳定性。实际的 ESI 势能（由独立的高压电源 HV2 提供为 2.0kV）范围为 2.1kV 至 4.5kV，具体取决于所施加的分离电压（由电源 HV1 提供的 12.0-20.0kV）和背景电解质（BGE）的电导率。当毛细管尖端与喷咀尖端对齐时，接口的稳定性得到了部分改善。然而，只有当毛细管尖端缩进喷咀 20μm 时，才能实现喷雾和分离电势的完全解耦。在这种设置下，ESI 势能稳定且独立于分离电势（电压）和 BGE 电导率。此外，与毛细管尖端与喷咀尖端对齐或突出喷咀尖端的设置相比，该设置为 CE-ESI-MS 对选定药物和苄基吡啶鎓阳离子的分析提供了更好的灵敏度。
