Multimode Collision Cell for Mass Spectrometer Interference
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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 operation in dual modes to selectively eliminate interferer ions using either kinetic energy discrimination or dynamic reaction cell techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If higher resolution mass analyzers are used to distinguish analyte ions from interferer ions, then spectral interference is reduced, but extraction rate decreases and ion signal loss increases
Solution Approach 1:
The patent applies preliminary action by reducing the kinetic energy of ions before they enter the mass analyzer through a collision cell. By performing energy reduction upstream, the system enables the use of lower resolution mass analyzers while still achieving effective separation of analyte and interferer ions, thus avoiding the need for high resolution analyzers that would reduce extraction rates.
Solution Approach 2:
The collision cell acts as an intermediary component between the ion source and mass analyzer. It mediates the ion beam by selectively reducing the energy of polyatomic interferer ions through collisions with neutral gas molecules, while allowing monatomic analyte ions to pass through with minimal energy loss. This intermediary step enables effective interference removal without requiring high resolution mass analysis.
2Measurement precision
If higher resolution mass analyzers are used to distinguish analyte ions from interferer ions, then spectral interference is reduced, but ion signal loss increases requiring more sensitive detectors
Solution Approach 1:
The collision cell performs preliminary energy reduction of interferer ions before mass analysis, eliminating the need for high resolution mass analysis. This preserves ion signals that would otherwise be lost in high resolution analyzers, reducing overall ion signal loss and detector requirements.
Solution Approach 2:
The patent converts the harmful effect of polyatomic interferer ions into a beneficial separation mechanism. By exploiting the difference in collisional cross-sections between polyatomic and monatomic ions, the system uses collision-induced energy reduction to selectively remove interferers while preserving analyte ions, turning a potential source of interference into a useful separation tool.
3Measurement precision
If kinetic energy discrimination is used to remove interferer ions, then detection limits improve, but ion transmission efficiency may be reduced
Solution Approach 1:
The patent applies local quality by creating different energy reduction conditions for different ion types within the collision cell. Polyatomic interferer ions experience significant energy reduction due to their larger collisional cross-sections, while monatomic analyte ions experience minimal energy loss. This localized differential treatment improves detection limits without significantly reducing overall ion transmission efficiency.
Solution Approach 2:
The system changes the kinetic energy parameter of ions selectively based on their mass and structure. By controlling the collision gas pressure and composition, the system optimizes the degree of energy reduction for interferer ions while maintaining adequate transmission of analyte ions, thus balancing detection limit improvement with transmission efficiency.
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, allowing for versatile operation that balances ion sensitivity and interference removal, enabling detection of ions at parts per trillion levels while minimizing the impact of non-spectral interferences.
Implementation Method 1
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 2
providing an inert gas within the pressurized cell, the inert gas being substantially non-reactive with ions of the first and second kinds, to 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
Data Source
AI summary
A mass spectrometer is provided that is configurable for operation in both a Kinetic Energy Discrimination (KED) mode and a dynamic reaction cell (DRC) mode. To operate in the KED mode, a collision cell can be filled with a quantity of the inert gas, and an energy barrier can be formed between the collision cell and a downstream mass analyzer. 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.