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Ion trajectory simulations of a conical octopole ion guide and its comparison with a parallel one in chemical ionization mass spectrometric applications
Author(s) -
Shao Qiduo,
Zhao Jun
Publication year - 2018
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.8129
Subject(s) - chemistry , ion , mass spectrometry , ion source , ionization , ion current , quadrupole mass analyzer , reflectron , conical surface , atomic physics , analytical chemistry (journal) , time of flight mass spectrometry , physics , materials science , organic chemistry , chromatography , composite material
Rationale Focusing and transmission are important characteristics of ion transportation in mass spectrometric applications. An ion guide device is an essential component in a mass spectrometer, especially when chemical ionization is employed. We present a conical octopole ion guide and its comparison with a parallel counterpart for simulating the ion trajectories through the ion guide and the quadrupole mass analyzer. Methods Ion trajectory simulations using SIMION 8.0 were performed to evaluate the performance of both conical and parallel octopole ion guides and the overall ion transmission through combining the octopole ion guide and the quadrupole mass analyzer in the mass spectrometer. Through the simulations, parameters that control the ion guide were optimized for the focus and transport of weakly bonded cluster ions, including the DC bias voltage, the frequency and the amplitude of the sine wave applied to the guide. Results The results from ion trajectory simulations showed that the ion beam can be highly focused from initially 10 mm down to 2 mm in diameter for the conical octopole ion guide. The transmission efficiencies are dependent on the mass of the ion, the frequency and amplitude of the radiofrequency waveform applied to the octopoles. The simulated overall transmission efficiencies of the conical ion guide are consistent with the observed sensitivities from the previously reported calibration experiments in the low‐mass region but are much higher than those in the high‐mass region (i.e., masses greater than 400 amu). Conclusions The simulations showed that the conical octopole ion guide can efficiently transport ions with high focusing through differentially pumped vacuum chambers. However, the overall transmission efficiencies of the conical octopole ion guide are in general lower than the parallel one when combined with the quadrupole mass analyzer based on the assumed exponential pressure gradient along the axial of the octopole ion guide.