Development and Parameter Optimization of Quadrupole Ion Collision Induced Dissociation System

Collision-induced dissociation (CID) is a core technique in tandem mass spectrometry that induces ion fragmentation to generate characteristic fragment ions for elucidating molecular structures and identifying target compounds. This study successfully developed a quadrupole ion collision system with dual-mode operation on a home-built quadrupole time-of-flight mass spectrometry platform. The ion collision system mainly consists of three components: the quadrupole collision cell, the power supply system, and the pressure control system. Among these, the quadrupole collision cell serves as the reaction zone where CID occurs. The power supply system is responsible for providing the radiofrequency and direct current voltages required to confine ions and initiate CID. The pressure control system is designed to precisely regulate the internal pressure of the collision cell, ensuring an appropriate supply of background collision gas. Through the coordinated optimization of these subsystems, efficient fragmentation of target ions and effective transmission of fragment ions have been successfully realized. Compared to conventional methods reliant on empirical parameters or trial-and-error optimization, this work realized the complete methodological transition and systematic parameter optimization from transient voltage mode to static voltage mode on a self-built platform. Through precise, stepwise adjustment of collision gas pressure (2×10⁻⁴ Pa), ion kinetic energy (30 eV), timing phase durations, and radio frequency (RF) voltage, a reproducible and repeatable parameter optimization workflow for collision-induced dissociation was established. Particularly, the proposed "transient-static" dual-mode collaborative verification mechanism effectively balances the controllability of the dissociation process and analytical throughput, offering a flexible and efficient strategy for complex sample analysis. In the static voltage mode, the MS/MS signal intensity of reserpine and its fragment ions was doubled compared to that in transient voltage mode, accompanied by significantly improved ion transmission efficiency and signal-to-noise ratio. This performance enhancement originates from the substantial reduction in ion loss and the continuity of the analytical process under the static voltage mode, demonstrating the distinct advantages of this study in improving mass spectrometry detection sensitivity and stability. This research has not only realized the independent development and closed-loop parameter optimization of the key collision system, but also endowed the entire instrument with high-performance tandem mass spectrometry capabilities, thus overcoming the long-standing technical bottleneck of dependence on imported or imitated modules. The established dual-mode collision methodology and optimization framework exhibit excellent transferability and extensibility, providing solid technical support and a practical example for advancing the localization of key mass spectrometer components and enhancing independent methodological development capabilities. It offers an important pathway for functional expansion and industrial upgrading of home-developed high-end mass spectrometers.