A Subtle Change in Nanoflow Rate Alters the Ionization Response As Revealed by Scanning Voltage ESI-MS
A Subtle Change in Nanoflow Rate Alters the Ionization Response As Revealed by Scanning Voltage ESI-MS
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DOI：
10.1021/acs.analchem.2c02997
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发表时间：
2022-11-09
影响因子：
7.4
通讯作者：
Chen, Lee Chuin
中科院分区：
文献类型：
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作者：
Han, Zhongbao;Chen, Lee Chuin
纳升/分钟流速下，纳米电喷雾电离（nanoESI）源产生的带电小液滴具有高性能电离的独特特性。在此范围内对流速进行连续扫描能够更详细地追踪液滴大小的影响，以便更好地理解电离过程。到目前为止，由于缺乏合适的液体泵以及基于微毛细管系统的重现性，这种实际应用受到了阻碍。在此，通过对电喷雾高压（HV）进行精确扫描，在几百皮升/分钟到接近100纳升/分钟的动态范围内，以连续变化的流速进行了离线纳米电喷雾质谱分析。其原理基于从具有已知喷雾电流 - 流速关系的大泰勒锥产生纳米电喷雾的新模式。由高压控制的瞬时流速通过同时测量喷雾电流来确定。该系统成功地应用于揭示纳流流速对蛋白质平均电荷态的作用、分析分析物混合物以及脱盐效果。通过使用具有高电导率的缓冲溶液，当将流速调节到低于约5纳升/分钟的阈值时，还观察到了一种高度可控的氧化修饰，这一发现对于按需氧标记具有潜在应用。
The small charged droplet generated from the nanoelectrospray ionization (nanoESl) source at nL/min flow rate gives its unique feature of high-performance ionization. A continuous scan of the flow rate in this regime can trace the effect of droplet size in greater detail for a better understanding of the ionization process. To date, such practical implementation is hindered by the lack of a suitable liquid pump and the reproducibility of microcapillaries-based systems. Here, offline nanoESl mass spectrometry with a continuously varying flow rate in a dynamic range of several hundred pL/min to similar to 100 nL/min was performed by the precision scanning of ESI high voltage (HV). The principle is based on the new paradigm of generating nanoelectrospray from a large Taylor cone with a known spray current-flow rate relationship. The instantaneous flow rate controlled by the HV was determined by simultaneous measurement of the spray current. The system is successfully applied to reveal the role of nanoflow rate on the average charge state of proteins, analysis of analyte mixture, and desalting effect. With the use of a buffer solution with high electric conductivity, a highly controllable oxidative modification was also observed by tuning the flow rate below a threshold of similar to 5 nL/min, a finding that has potential application to on-demand oxygen labeling.