Research of Unidirectional Ion Ejection in Printed-Circuit-Board Ion Trap / 分析化学

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.

Performance Investigation of Ion Trap with Various Collision gas and Pressures / 分析化学

Ion trap performances are investigated based on digital ion trap technique with different collision gases at different pressures. Collision gases of helium (4 amu), nitrogen (28 amu) and argon (40 amu) with various pressures are adopted in ion excitation and dissociation stages to investigate the ion trap performances, including mass resolution, signal intensity, tandem mass spectrometric analysis ability and low-mass cut off (LMCO) effect. It is found that when heavy gas of argon is used, energy can be efficiently transferred and LMCO effect is decreased with higher ion capture and dissociation efficiencies but with low mass resolution. Higher mass resolution is realized with helium as collision gas. Furthermore, at the same gas pressure, heavy gas is beneficial to abundant fragment ions and structural information of precursor ion.

Structure and Property of Ladder Electrode Linear Ion Trap Mass Analyzer / 分析化学

Theoretical study and experimental test of a new ion trap mass analyzer-ladder electrode linear ion trap (LeLIT) were reported. The LeLIT was composed of two pairs of ladder electrodes and one pair of end-electrodes. By optimizing the geometric structure of ladder electrodes, we optimized the electric field distribution for optimum mass analysis. Since the distribution of electric field can be controlled by the adjustment of LeLIT structure, LeLIT have better performance than rectilinear ion trap theoretically. Due to its simpler structure than hyperbolic electrode LIT, LeLIT can be easily built. In this work, the height, width and field ratio were adjusted for optimizing the property of LeLIT, and a mass resolution of 10150 was obtained when the mass scan speed was 225 Da / s for a LeLIT with X0 ×Y0 = 9 mm×5 mm dimension. The preliminary experimental result showed that the LeLIT has proper tandem mass spectrometric performance as any conventional ion trap mass analyzer.

Optimization of Performance of Toroidal Ion Trap with Triangular Electrode by Theoretical Simulation / 分析化学

The toroidal ion trap is an ideal candidate for miniaturized ion trap because it has much higher ion trapping capacity than a standard quadrupole ion trap of equal trapping dimensions. A novel toroidal ion trap mass analyzer with triangular electrode which contained a filament end cap, a detector endcap, an inner ring and an outer ring was reported. After designing and optimizing the electrodes by theoretical simulations, we found that the asymmetric triangle electrodes could reduce the affection from toroidal shape and improve the ion ejection rate and the mass resolution of the ion trap. The best design of the toroidal ion trap with a mass resolution of 1486 at m/z 609 was obtained.

Improvement of Low Mass Cutoff Effect Using Digital Ion Trap Technology / 分析化学

The low mass cutoff ( LMCO) is the main weakness of ion trap when it performs tandem mass analysis by collision induced dissociation (CID). LMCO means that some daughter ions of m/ z are less than about 1 / 3 of the m/ z of parent ion could not be detected during the tandem mass spectrometry processing. A new method which can significantly improve the effect of low mass cutoff was proposed and investigated. By simply changing the scan method of digital potential frequency, some low mass ions can be effectively observed during the tandem mass spectrometric experiment. In the experiment, the frequency of the digital ion trapping power and ion activation power were scanned from lower value to higher value, and some lower mass product ions could be detected during CID process. For example, some lower mass ions were observed during the CID of reserpine precursor ion when the frequency of its digital trapping power was scanned from 500 kHz to 560 kHz. The tandem mass spectra of Reserpine ion showed that the experimental results both from this work and the triple quadrupole mass spectrometer were exactly the same.