Xiaoyu Zhou1,2, Zheng Ouyang1,2. 1. State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, Beijing, 100084, China. 2. Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, 47907, USA.
Abstract
RATIONALE: The ion transfer from the atmospheric pressure ion source to mass spectrometer inlet is directly related to the sensitivity of the mass spectrometry (MS) analysis. Electric field and dynamic gas flow are typically used to facilitate the ionization process and ion transfer. While sophisticated methods have been developed for ion trajectory simulation with a pure electric field, the influence of the dynamic gas flow could not be easily incorporated for the study. METHODS: A nanoESI (electrospray ionization) source was set off-axis in front of an MS inlet to study the ion transfer under the influence of both electric field and gas flows. Electro-hydrodynamic simulation (EHS) was performed to predict the ion transfer, which was subsequently validated with the experimental characterization. RESULTS: The EHS results based on the gas dynamics were found to match well with the experimental results and therefore can be used to guide the instrumentation design. The relative intensities of different ion species could be modified by adjusting the gas flow rate, and a differential transfer of the selected ion species was achieved. CONCLUSIONS: EHS is a powerful tool for the design of ion optics operating at atmospheric pressure. As a rapid and convenient method, proper combination of an air dynamic field and an electric field enabled a gas-phase ion separation in the source region without using sophisticated ion mobility devices.
RATIONALE: The ion transfer from the atmospheric pressure ion source to mass spectrometer inlet is directly related to the sensitivity of the mass spectrometry (MS) analysis. Electric field and dynamic gas flow are typically used to facilitate the ionization process and ion transfer. While sophisticated methods have been developed for ion trajectory simulation with a pure electric field, the influence of the dynamic gas flow could not be easily incorporated for the study. METHODS: A nanoESI (electrospray ionization) source was set off-axis in front of an MS inlet to study the ion transfer under the influence of both electric field and gas flows. Electro-hydrodynamic simulation (EHS) was performed to predict the ion transfer, which was subsequently validated with the experimental characterization. RESULTS: The EHS results based on the gas dynamics were found to match well with the experimental results and therefore can be used to guide the instrumentation design. The relative intensities of different ion species could be modified by adjusting the gas flow rate, and a differential transfer of the selected ion species was achieved. CONCLUSIONS: EHS is a powerful tool for the design of ion optics operating at atmospheric pressure. As a rapid and convenient method, proper combination of an air dynamic field and an electric field enabled a gas-phase ion separation in the source region without using sophisticated ion mobility devices.