A Simulation Model for Ion Motion in Quadrupole Field Based on COMSOL

Quadrupole mass spectrometer is currently one of the most widely used small-scale mass spectrometry instruments. Studying the ions trajectory in a quadrupole field is very important for a deeper understanding of the behavior of ions in quadrupole field, which not only helps to propose new scientific and technological issues in mass spectrometry, but also has practical guidance for the development of instruments. The digital simulation of ions trajectory is an efficient mean for studying the motion of ions in quadrupole field. In this paper, a digital simulation model of quadrupole field, namely Sim-Quaq-COM-V1.0, was established based on COMSOL Multiphysics. The simulation results of the model are in good agreement with the theoretical calculation results, and it can be used as an accurate digital model to study the behavior of ions in quadrupole fields. On this basis, the motion behavior of ions in the hyperbolic quadrupole and the cylindrical quadrupole were compared, and the number of m/z 69 ions passing through the hyperbolic quadrupole field is about 4 times that of the cylindrical quadrupole field under the same conditions. The model has three advantages. Firstly, the self-designed general geometric model and grid were adopted as the built-in model, which can be used to simulate the cylindrical quadrupole field and hyperbolic quadrupole field of various geometric sizes. The modular design is simple and clear. Users only need to modify the geometric parameters and mesh parameters to generate the corresponding geometric model and high-precision mesh. Secondly, the parameters of the model could be configured uniformly in a text file, and the model parameters could be adjusted in batches by modifying the text file. Lastly, the function of multi-core and cluster in COMSOL were utilized to achieve large-scale parallel computing through multi-CPU server and quickly process a large number of ions at the same time. Compared with other models like the default COMSOL model for cylindrical quadrupole field, the simulation speed and accuracy of this model are improved. Through the simulation calculation model, the time of geometric design and modeling is saved, the global parameters can be quickly configured, and the difficulty of calculation is reduced. The model supports parallel computing technology. It is greatly improved in terms of calculation speed and calculation amount, thus can process a large number of ions at the same time, shorten the research cycle, and help the digital development of mass spectrometer design and research technology.