PCB分压离子阱性能优化的理论模拟研究

Theoretical Research on Performance Optimization of PCB Voltage-Divided Ion Trap Mass Analyzer

  • 摘要: 印刷线路板(Printed-Circuit-Board,以下简称PCB)分压离子阱是一种主要由印刷线路板围成的新型简单电极结构的质量分析器。PCB分压离子阱的尺寸小巧、加工装配容易且成本较低,适于用作小型化离子阱质谱仪的质量分析器。为进一步提高PCB分压离子阱的分析性能,本研究对原有的PCB分压离子阱的电压施加方式与几何结构进行改进。利用计算机模拟软件SIMION和AXSIM,分析了分压离子阱的内部电场、离子运动轨迹及模拟质谱峰图。模拟中分别采用m/z 4 000、4 001和4 002离子,结果显示在射频信号(RF)分压比不变的情况下,不同的共振激光信号(AC)分压比对质量分辨率有显著的影响。随着该分压比的减小,质量分辨率得到相应的提高。当仅在中央电极施加AC信号时,可将质量分辨率提高约25%。另一方面,撤除角接地电极的新型PCB分压离子阱结构的性能较原有PCB分压离子阱的性能更优,对于m/z 4 001离子,其质量分辨率可以达到10 325。该结果可为进一步的实验提供理论基础。

     

    Abstract: Printed-circuit-board voltage-divided ion trap (PCBVDIT) is a novel mass analyzer with simple electrode structure, mainly composed of printed circuit boards. PCBVDIT is a good choice for the analyzer of miniaturized ion trap mass spectrometer for the reason that PCBVDIT has a compact size, easy process and assembly technology and low cost. The operation mode and geometry structure of a prototype PCBVDIT were improved in order to enhance its analytical performance. The internal electric field distribution of PCBVDIT was calculated by PAN_33. Ion trajectories inside the PCBVDIT and simulated mass spectrum peaks for different electrode structures besides different operation modes were both simulated by software SIMION and AXSIM. The ions used in the simulation experiments were m/z 4 000, 4 001 and 4 002. It shows that different voltage-divided ratios of supplement resonance signal has a significant influence on the resolving power of PCBVDIT, even though the voltage-divided ratio of radio frequency trapping waveform remains unchanged. With the reduction of voltage-divided ratio of supplement resonance signal, mass resolution could be improved. In the limit case, mass resolution would be improved by about 25% when the supplement resonance signal was only applied to the central electrode, that is, the voltage-divided ratio of supplement resonance signal was equal to zero. On the other hand, enhanced performance, with a mass resolution up to 10 325 for the ions which had the mass-to-charge ratio of 4 001, could be acquired on the structure-optimized PCBVDIT by removing the corner electrodes from the prototype. These simulated results could provide a theoretical foundation for further investigations.

     

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