Gigaohm and Teraohm Resistors in Femtoamp and Picoamp Electrospray Ionization
Gigaohm and Teraohm Resistors in Femtoamp and Picoamp Electrospray Ionization
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DOI：
10.1021/jasms.2c00369
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发表时间：
2023-04-13
影响因子：
3.2
通讯作者：
Li，Anyin
中科院分区：
文献类型：
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作者：
Allen，Nicholas;Li，Huishan;Li，Anyin
飞秒安培电喷雾电离（femtoESI）模式已被证明具有独特的特性，可以促进电离效率的研究和实验，需要低离子束通量。femtoESI的研究受到10-100 V的微小外加电压窗口的阻碍，超过该电压窗口，电离电流迅速跳到纳安。该窗口难以定位，因为精确的起始电压由于离子源对准的变化而波动。串联的大电阻（0.1-100 TΩ）有效地扩展了femtoESI施加的电压范围，最高可达1400 V。通过交换电阻，快速交替允许在相同对准下比较两种ESI模式。在肽混合物中，具有较低表面活性的分析物在nanoESI模式中被抑制，而femtoESI模式显示出较低表面活性物质的信号增强。对于蛋白质溶液，所产生的电荷状态几乎没有变化，但femtoESI模式确实显示出蛋白质峰的平均电荷状态降低。与nanoESI模式操作相比，在特定电荷状态下，在femtoESI模式下分析的肽和蛋白质也倾向于产生比质子化峰更高强度的钠化峰。
The femtoamp electrospray ionization (femtoESI) mode has been shown to exhibit unique characteristics that may facilitate ionization efficiency studies and experiments requiring low ion beam flux. Investigation of femtoESI was hindered by a tiny, applied voltage window of 10–100 V, beyond which ionization currents quickly jumped to nanoamps. This window was difficult to locate because the exact onset voltage fluctuates due to variations in ion source alignments. Large resistors (0.1–100 TΩ) in series effectively expanded the femtoESI applied voltage range, up to 1400 V. By swapping resistors, rapid alternation allows for the comparison of both ESI modes under the same alignment. In peptide mixtures, analytes with lower surface activity are suppressed in the nanoESI mode whereas the femtoESI mode shows signal enhancement of less surface-active species. For protein solutions, there is little change in the charge states generated but the femtoESI mode does show a decrease in the average charge state of protein peaks. Peptides and proteins analyzed in the femtoESI mode also tend to generate higher intensity sodiated peaks over protonated peaks at specific charge states compared with nanoESI mode operation.