Li Mengtian, Li Huishan, Allen Nicholas R, Wang Taoqing, Li Linfan, Schwartz Jae, Li Anyin
Department of Chemistry, University of New Hampshire 23 Academic Way Durham NH 03824 USA
Thermo Fisher Scientific 355 River Oaks Pkwy San Jose CA 95134 USA.
Chem Sci. 2020 Dec 22;12(5):1907-1914. doi: 10.1039/d0sc06221a.
On-demand electrospray ionization from different liquid channels in the same emitter was realized using filamented capillary and gas phase charge supply. The solution sub-channel was formed when back-filling solution to the emitter tip by capillary action along the filament. Gas phase charge carriers were used to trigger electrospray ionization from the solution meniscus at the tip. The meniscus at the tip opening may be fully filled or partially empty to generate electrospray ionization in main-channel regime and sub-channel regime, respectively. For emitters with 4 μm tip opening, the two nested electrospray (nested-ESI) channels accommodated ESI flow rates ranging from 50 pL min to 150 nL min. The platform enabled on-demand regime alternations within one sample run, in which the sub-channel regime generated smaller charged droplets. Ionization efficiencies for saccharides, glycopeptide, and proteins were enhanced in the sub-channel regime. Non-specific salt adducts were reduced and identified by regime alternation. Surprisingly, the sub-channel regime produced more uniform responses for a peptide mixture whose relative ionization efficiencies were insensitive to ESI conditions in previous picoelectrospray study. The nested channels also allowed effective washing of emitter tip for multiple sampling and analysis operations.
利用丝状毛细管和气相电荷供应实现了同一发射器中不同液体通道的按需电喷雾电离。当溶液通过毛细管作用沿细丝向发射器尖端回注时，形成溶液子通道。气相电荷载流子用于触发尖端溶液弯月面的电喷雾电离。尖端开口处的弯月面可以完全充满或部分为空，分别在主通道模式和子通道模式下产生电喷雾电离。对于尖端开口为4μm的发射器，两个嵌套的电喷雾（nested-ESI）通道的电喷雾流速范围为50 pL/min至150 nL/min。该平台能够在一次样品运行中实现按需模式切换，其中子通道模式产生较小的带电液滴。在子通道模式下，糖类、糖肽和蛋白质的电离效率得到提高。通过模式切换减少并识别了非特异性盐加合物。令人惊讶的是，对于肽混合物，子通道模式产生了更均匀的响应，其相对电离效率在之前的皮升电喷雾研究中对电喷雾条件不敏感。嵌套通道还允许对发射器尖端进行有效清洗，以进行多次采样和分析操作。
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