Gimelshein Natalia, Gimelshein Sergey, Lilly Taylor, Moskovets Eugene
J Am Soc Mass Spectrom. 2014 May;25(5):820-31. doi: 10.1007/s13361-014-0838-7.
Gas and ion transport in the capillary-skimmer subatmospheric interface of a mass spectrometer, which is typically utilized to separate unevaporated micro-droplets from ions, was studied numerically using a two-step approach spanning multiple gas dynamic regimes. The gas flow in the heated capillary and in the interface was determined by solving numerically the Navier-Stokes equation. The capillary-to-skimmer gas/ion flow was modeled through the solution of the full Boltzmann equation with a force term. The force term, together with calculated aerodynamic drag, determined the ion motion in the gap between the capillary and skimmer. Three-dimensional modeling of the impact of the voltage applied to the Einzel lens on the transmission of doubly charged peptide ions through the skimmer orifice was compared with experimental data obtained in the companion study. Good agreement between measured and computed signals was observed. The numerical results indicate that as many as 75% of the ions that exit from the capillary are lost on the conical surface of the skimmer or capillary outer surface because of the electrostatic force and plume divergence.
质谱仪的毛细管 - 分离器亚大气压界面中的气体和离子传输通常用于从离子中分离未蒸发的微滴，本研究采用跨越多种气体动力学状态的两步法进行了数值模拟。通过对纳维 - 斯托克斯方程进行数值求解，确定了加热毛细管和界面中的气流。通过求解带有力项的完整玻尔兹曼方程，对毛细管到分离器的气体/离子流进行了建模。该力项与计算出的空气动力学阻力一起，决定了毛细管和分离器之间间隙中的离子运动。将施加到单透镜上的电压对双电荷肽离子通过分离器孔口传输的影响的三维建模与在配套研究中获得的实验数据进行了比较。观察到测量信号与计算信号之间有良好的一致性。数值结果表明，由于静电力和羽流发散，从毛细管中出来的离子多达75%在分离器的锥形表面或毛细管外表面上损失。
