Chang Ching-Han, Urban Pawel L
Department of Chemistry, National Tsing Hua University, Hsinchu 300044, Taiwan.
ACS Omega. 2024 Oct 11;9(42):43211-43218. doi: 10.1021/acsomega.4c07653. eCollection 2024 Oct 22.
Electrospray ionization (ESI) remains the dominant technique in mass spectrometry (MS)-based analyses. Here, we investigated the relationship between a crucial aspect of ESI, the formation of the Taylor cone, and the MS ion current by utilizing a triple quadrupole (QqQ) mass spectrometer coupled with a streaming high-speed camera and a 3-ring electrode system. In one test, ion current over a 30-s plume gate (a ring electrode) opening was compared with the Taylor cone occurrence analyzed offline, with Spearman's correlation coefficients consistently near 0 despite parameter variations. In another test, real-time detection of Taylor cones was synchronized with QqQ-MS, selectively opening (de-energizing) the plume gate based on the Taylor cone status. This approach enabled matching the ion current with the Taylor cone occurrence. There was no apparent difference between the MS signals recorded in the presence and absence of a Taylor cone. Additionally, a Faraday plate was employed as a detector in offline experiments, revealing agreement between the frequency of liquid meniscus (Taylor cone) oscillation (∼1.92 kHz)-measured by high-speed imaging-and the frequency of spray current (∼1.93 kHz). We suggest that the lack of positive correlations in the MS experiments is due to intrinsic ion carryover during transit from the ion source to the detector and due to the insufficient data acquisition rate of the mass spectrometer, which erases short-term fluctuations of ion current.
电喷雾电离（ESI）仍然是基于质谱（MS）分析中的主导技术。在此，我们利用一台串联四极杆（QqQ）质谱仪，结合流式高速摄像机和三环电极系统，研究了ESI的一个关键方面——泰勒锥的形成与MS离子流之间的关系。在一项测试中，将30秒的羽流栅（一个环形电极）打开期间的离子流与离线分析的泰勒锥出现情况进行了比较，尽管参数有所变化，但斯皮尔曼相关系数始终接近0。在另一项测试中，泰勒锥的实时检测与QqQ-MS同步，根据泰勒锥状态选择性地打开（断电）羽流栅。这种方法能够使离子流与泰勒锥的出现情况相匹配。在有和没有泰勒锥的情况下记录的MS信号之间没有明显差异。此外，在离线实验中使用法拉第板作为检测器，结果表明通过高速成像测量的液体弯月面（泰勒锥）振荡频率（约1.92千赫兹）与喷雾电流频率（约1.93千赫兹）之间具有一致性。我们认为，MS实验中缺乏正相关是由于离子从离子源传输到检测器过程中的固有离子残留，以及质谱仪的数据采集速率不足，从而消除了离子流的短期波动。
