Multimode Collision Cell for Mass Spectrometer Interferer Suppression
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Solution Overview
Problem
Mass spectrometry systems face challenges in distinguishing between analyte ions and unwanted interferer ions with similar or close mass-to-charge ratios, leading to spectral interference, and are also affected by non-spectral interferences such as neutral metastable species, photons, and gas molecules, which degrade detection limits and require higher resolution and more sensitive detectors.
Innovation Solution
A mass spectrometer system and method that utilizes a pressurized quadrupole cell with an inert gas to collide with ions, differentially reducing the energy of interferer ions with larger collisional cross-sections, and an energy barrier to prevent their transmission, allowing for dual-mode operation between collision and reaction modes to selectively eliminate interferer ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If higher resolution mass analyzers are used to distinguish analyte ions from interferer ions, then measurement precision is improved, but productivity decreases due to slower extraction rates and higher ion signal loss
Solution Approach 1:
A collision cell filled with inert gas (e.g., helium) is introduced as an intermediary component between the ion source and mass analyzer. This collision cell performs kinetic energy discrimination by allowing interferer ions to collide with gas molecules and lose kinetic energy, while analyte ions pass through with minimal energy loss. This mediator enables separation of ions based on collisional cross-section differences without requiring higher mass resolution, thus maintaining extraction rate and productivity.
Solution Approach 2:
The system changes the energy parameter of ions by introducing a collision cell where ions undergo kinetic energy discrimination. By controlling the gas pressure and composition in the collision cell, the system selectively reduces the kinetic energy of interferer ions (which have larger collisional cross-sections) while maintaining the energy of analyte ions. This parameter change enables differentiation of ions with similar m/z ratios without increasing mass resolution requirements.
2Measurement precision
If higher resolution mass analyzers are used to reduce spectral interference, then measurement precision is improved, but loss of substance increases due to higher ion signal loss
Solution Approach 1:
The collision cell acts as an intermediary that selectively removes interferer ions through kinetic energy discrimination before they reach the mass analyzer. By using inert gas molecules as mediators for energy transfer, the system preferentially slows down interferer ions (with larger collisional cross-sections) while allowing analyte ions to pass through. This reduces spectral interference and ion signal loss by eliminating interferers upstream rather than relying on high-resolution separation that would require longer analysis times and result in more ion loss.
3Measurement precision
If kinetic energy discrimination is used to suppress interferer ions, then measurement precision is improved, but device complexity increases due to additional cell components
Solution Approach 1:
The collision cell is designed to perform multiple functions: it serves as both a kinetic energy discrimination device for suppressing interferer ions and as a transmission pathway for analyte ions to the mass analyzer. By integrating these functions into a single component rather than adding separate suppression devices, the system achieves interferer ion suppression while minimizing additional complexity. The collision cell can be configured within existing mass spectrometer architectures, reducing overall system complexity.
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 approach effectively suppresses unwanted ions, improving detection limits and reducing spectral interference, while maintaining ion sensitivity and versatility in operating modes, allowing for both kinetic energy discrimination and dynamic reaction cell functionalities within a single system.
Implementation Method 1
collide with a first proportion of the first group of ions and a second proportion of the second group of ions, the first proportion being substantially greater than the second proportion, to reduce the energies of the individual ions in the first group of ions to a greater extent than in the second group of ions
Implementation Method 2
supplying an RF voltage to the quadrupole rod set to form a quadrupolar field therewithin for radial confinement of ions being transmitted from the entrance end to an exit end of the pressurized cell
Implementation Method 3
providing an exit barrier at the exit end of the pressurized cell of a strength selected to prevent a larger proportion of the reduced energy ions in the first group of ions than in the second group of ions from penetrating the exit barrier
Data Source
AI summary
A mass spectrometer system is provided that is configurable for operation in both a Kinetic Energy Discrimination (KED) and Dynamic Reaction Cell (DRC). A pressurized or collision cell included in the mass spectrometer encloses a quadrupole and is coupled to a source of both inert and reactive gas. To operate in the KED mode, the collision cell can be filled with a quantity of the inert gas and an energy barrier formed between the collision cell and a downstream mass analyzer. Interferer ions collided with the inert gas can lose on average more energy relative to analyte ions of the same mass to charge ratio and can thus be trapped by the energy barrier in greater proportions. To operate instead in the DRC mode, the collision cell can be filled with a quantity of gas that is reactive with the interferer ions only. Mass filtering of the product ions can then transmit proportionally more of the analyte ions to the downstream mass analyzer. A mode controller coordinates the two modes of operation.