Electrospray ionization is commonly employed in modern mass spectrometry experiments for applications ranging from proteomics to environmental science and for fundamental studies of the chemical reactivity of ions. Despite the ubiquity of electrospray ionization, the total ion currents achieved using the technique remain relatively poor. While there are significant losses within the atmospheric pressure interface of the mass spectrometer (MS), many ions are lost due to space charge repulsion before ions and charged microdroplets enter the instrument. Space charge effects also limit the extent to which multiplexing of electrosprays can be used to increase ion currents. In this work, a flow of oppositely charged ions produced by atmospheric pressure chemical ionization (APCI) is employed to mitigate space charge effects in an analyte ion beam produced by nanoelectrospray ionization (nESI) as it is passed through an atmospheric pressure ion guide outside of a mass spectrometer. A decrease in the nESI beam width together with an increase in peak intensity is observed using an ion charge coupled detector in the presence of a counterflow of ions of the opposite charge. This result indicates that focusing occurs in the ion guide. Measurements of the space charge compensated ion beam using an Agilent Ultivo triple quadrupole mass spectrometer are correlated with changes in ion focusing, indicating that space charge compensation occurring before the ion beam enters the mass spectrometer can increase detected ion currents.

电喷雾电离通常用于现代质谱实验，其应用范围从蛋白质组学到环境科学以及离子化学反应性的基础研究。尽管电喷雾电离无处不在，但使用该技术获得的总离子电流仍然相对较差。虽然质谱仪 (MS) 的大气压力界面内有大量损失，但在离子和带电微滴进入仪器之前，由于空间电荷排斥，许多离子会丢失。空间电荷效应也限制了电喷雾多路复用可用于增加离子电流的程度。在这项工作中，由大气压化学电离 (APCI) 产生的带相反电荷的离子流用于减轻纳米电喷雾电离 (nESI) 产生的分析物离子束中的空间电荷效应，因为它通过质谱仪外部的大气压离子导向器。在存在相反电荷离子的逆流的情况下，使用离子电荷耦合检测器观察到 nESI 光束宽度的减小以及峰值强度的增加。该结果表明在离子导向器中发生了聚焦。使用 Agilent Ultivo 三重四极杆质谱仪对空间电荷补偿离子束的测量与离子聚焦的变化相关，表明在离子束进入质谱仪之前发生的空间电荷补偿可以增加检测到的离子电流。