Wilkes J G, Freeman J P, Heinze T M, Lay J O, Vestal M L
USFDA, National Center for Toxicological Research, Jefferson, Arizona 72079.
Rapid Commun Mass Spectrom. 1995;9(2):138-42. doi: 10.1002/rcm.1290090207.
An AC corona-discharge device was inserted upstream of a thermospray vaporizer tip in a liquid chromatography/particle beam mass spectrometer to neutralize static aerosol charging. Response of a test analyte was measured with or without discharge initiation. If the solvent contained no ammonium acetate buffer, increased analyte signal was associated with the discharge. However, in the presence of ammonium acetate the benefit of AC discharge neutralization was either not observed or was more subtle. This led to the conclusion that the previously observed ammonium acetate "carrier" effect is attributable, at least in part, to neutralization of static electric charges produced spontaneously during the solvent nebulization process. In a second experiment, the pattern of particles issuing from the system momentum separator was examined by aiming the particle beam at a cold target located within a mass spectrometer ion source. Variations in particle density were observed depending on (i) whether or not the aerosol had been neutralized and (ii) the proximity of electron-beam-collimating magnets to the particle beam trajectory. These results are consistent with a hypothesis that electrostatic charging occurs spontaneously during the nebulization process in which an aerosol is formed from the high performance liquid chromatography effluent. Such electrostatic charging introduces a factor likely to degrade system performance by at least two modes: through interactions of the charged aerosol particles (i) with the walls of the aerosol transmission pathway, and, after they are accelerated into a particle beam and introduced into the mass spectrometer, (ii) with the magnets used for electron beam collimation in many mass spectrometer ion sources.
在液相色谱/粒子束质谱仪的热喷雾汽化器尖端上游插入一个交流电晕放电装置，以中和静态气溶胶充电。在有或没有放电启动的情况下测量测试分析物的响应。如果溶剂中不含醋酸铵缓冲液，分析物信号的增加与放电有关。然而，在存在醋酸铵的情况下，交流放电中和的益处要么未被观察到，要么更为微妙。这导致得出结论，先前观察到的醋酸铵“载体”效应至少部分归因于溶剂雾化过程中自发产生的静电荷的中和。在第二个实验中，通过将粒子束对准位于质谱仪离子源内的冷靶，检查了从系统动量分离器发出的粒子模式。观察到粒子密度的变化取决于（i）气溶胶是否已被中和，以及（ii）电子束准直磁体与粒子束轨迹的接近程度。这些结果与一个假设一致，即在由高效液相色谱流出物形成气溶胶的雾化过程中会自发发生静电充电。这种静电充电引入了一个可能通过至少两种模式降低系统性能的因素：通过带电气溶胶粒子（i）与气溶胶传输路径壁的相互作用，以及在它们被加速成粒子束并引入质谱仪后，（ii）与许多质谱仪离子源中用于电子束准直的磁体的相互作用。
