MS/MS Mass Spectrometer Collision Cell Gas Conductance Gradient
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Solution Overview
Problem
Conventional MS/MS mass spectrometers experience a decline in detection sensitivity and the emergence of ghost peaks due to ion delay and retention in the collision cell, particularly when used in chromatographic analysis, where ions lose kinetic energy and fail to reach the detector in a timely manner.
Innovation Solution
The MS/MS mass spectrometer design incorporates a collision cell with a smaller gas conductance at the ion injection end face compared to the exit end face, creating a gas flow that aligns with the ion passage direction, promoting ion transport and preventing ion delay by using a simple rod electrode ion guide structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ions travel through a long collision cell with high gas pressure to achieve sufficient dissociation, then dissociation efficiency is improved, but ion delay and kinetic energy loss increase causing detection sensitivity deterioration
Solution Approach 1:
The patent applies pneumatic principles by introducing a gas flow system into the collision cell. A gas inlet positioned at the precursor ion injection end creates a unidirectional gas flow that pushes ions through the collision cell, reducing ion delay while maintaining sufficient dissociation efficiency. The gas flow velocity and pressure are controlled to optimize both dissociation and ion transmission timing.
Solution Approach 2:
The patent implements dynamic control of gas pressure and flow rate in the collision cell. By dynamically adjusting the gas flow conditions, the system can optimize the balance between dissociation efficiency and ion transit time, preventing ion delay while ensuring adequate collision-induced dissociation occurs.
2Reliability
If gas pressure in the collision cell is increased to enhance dissociation, then dissociation efficiency improves, but ion kinetic energy attenuation increases causing ions to slow down and potentially halt
Solution Approach 1:
The patent uses a controlled gas flow system where gas is introduced at the injection end and exits at the product ion extraction end. This creates a unidirectional flow that maintains ion forward momentum while providing sufficient gas density for dissociation. The gas flow continuously replenishes kinetic energy to ions, preventing them from halting despite high gas pressure conditions.
Solution Approach 2:
The patent optimizes gas pressure parameters by maintaining a pressure gradient along the ion path, with higher pressure at the injection end and lower pressure at the extraction end. This parameter variation ensures sufficient dissociation collisions while allowing ions to maintain adequate speed for timely detection.
3Reliability
If the collision cell dimension along the ion optical axis is increased to improve dissociation, then dissociation efficiency improves, but the analysis time increases causing ghost peaks and detection sensitivity loss
Solution Approach 1:
The patent introduces a gas flow system that creates a virtual reduction in cell length by pushing ions through the collision region more rapidly. The gas flow velocity is optimized to match the ion velocity, creating a co-moving reference frame that effectively shortens the interaction time while maintaining dissociation efficiency, thus reducing ghost peaks and improving analysis speed.
4Measurement precision
If conventional quadrupole electrodes with DC and RF voltages are used for ion selection, then mass resolution is maintained, but ion transmission efficiency decreases due to ion delay in the collision cell
Solution Approach 1:
The patent compensates for ion delay caused by conventional quadrupole electrode systems by introducing a gas flow that actively transports ions through the collision cell. This pneumatic assistance ensures that ions maintain their temporal separation and mass resolution characteristics while improving overall transmission efficiency by reducing the effective residence time in the collision region.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances ion transmission efficiency, reduces ghost peaks, and maintains high detection sensitivity by ensuring ions are swiftly transported through the collision cell and into the detector, while simplifying the structure and reducing costs.
Implementation Method 1
a collision cell (20) for dissociating the precursor ions by making the precursor ions collide with a collision-induced dissociation (CID) gas
Implementation Method 2
the gas conductance on a side of an injection end face of the collision cell having an ion injection aperture for injecting ions into the collision cell is made smaller than the gas conductance on a side of an exit end face of the collision cell having an ion exit aperture for discharging ions from the collision cell so as to produce, in the collision cell, a flow of the CID gas having a component of flow vector in the same direction as the passage direction of the ions
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
The gas conductance on the ion injection side of a collision cell is made larger than the gas conductance on the ion exit side by providing two ion injection apertures 23, 25 in the collision cell. Due to the different gas conductances, a CID gas supplied through the gas supply tube 31 generally flows in a detection from the ion injection side to the ion exit side in the collision cell, namely, in the ion's passage direction. When the ions injected in the collision cell 20 slow down upon contacting with the CID gas, their progress is assisted by the gas flow, so that the delay of the ions in the collision cell 20 is alleviated. As a result, it is possible to avoid a deterioration in the detection sensitivity of a target product ion and to prevent a ghost peak caused by the stay of the ions.