印刷线路板分压离子阱的离子单向出射性能研究

印刷线路板(Printed-Circuit-Board,PCB)分压离子阱是一种新型质量分析器,其突出优点在于内部电场可通过调节射频分压比进行优化.本实验在PCB分压离子阱离子出射方向的两组离散电极上配置了非对称的射频分压,以引入奇次阶场成分,使得射频电场的场中心(即离子运动中心)发生偏移,从而实现离子单向出射.通过数值计算软件SIMION和AXSIM分析了射频分压比差值与其内部电场分布的关系,并模拟离子运动轨迹,得到离子出射情况和模拟质谱峰.模拟结果表明,当两组离散电极的射频分压比差值为20％时,在合适的AC频率条件下,对于m/z=609 Th的离子,PCB分压离子阱的离子单向出射率可达90％以上,且质量分辨率大于2500.本研究可使PCB分压离子阱在基本不损失质量分辨率和使用单检测器模式下,大幅提高离子检测效率,因而在小型化质谱仪应用中具有显著优势.

Research of Unidirectional Ion Ejection in Printed-Circuit-Board Ion Trap

Printed-circuit-board ion trap (PCBIT) is a novel ion trap mass analyzer,which is capable of optimizing its internal electric field distributions by adjusting the radio frequency (RF) voltage-divided ratio to improve its analytical performance.This work introduced odd electric field components into the trapping volume to achieve unidirectional ion ejection by applying asymmetric RF voltages to x electrode pairs of PCBIT.In this case,the center of ion vibration was displaced away from the geometrical center of PCBIT and ions were ejected predominantly through one of x electrode pairs.The relationship between asymmetric voltage-divided ratio (AV) and internal electric field distributions was investigated by simulation software SIMION and AXSIM.At the same time,the ion trajectories and simulated mass spectrum peaks were calculated.The results showed that,for ions with m/z 609 Th,a mass resolution over 2500 and an ion unidirectional ejection efficiency of over 90％ were achieved in PCBIT with AV=20％ at an appropriate frequency of AC.Using this method,ion unidirectional ejection efficiency of PCBIT can be significantly improved while maintaining a high mass resolution,which makes the PCBIT more suitable for developing miniaturized mass spectrometer.