Tandem Ion Trap for Selective Low m/z Extraction
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Solution Overview
Problem
Conventional mass spectrometry methods, such as collision-induced dissociation (CID), face challenges in studying post-translational modifications like glycosylation and phosphorylation due to the loss of post-translational moieties during fragmentation, and electron capture dissociation (ECD) and electron transfer dissociation (ETD) methods suffer from efficiency issues with precursor ion dissociation and secondary reactions.
Innovation Solution
A method involving a mass spectrometer with tandem multipole rod sets, where a radial RF potential and a DC potential are applied to generate a radial trapping potential and axial bias, allowing for selective extraction of ions based on m/z ratios without resonant excitation, thereby preventing the loss of product ions and reducing secondary reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resonant excitation is used to extract low m/z ions from a reaction cell, then low m/z ions can be mass selectively extracted, but collision induced dissociation (CID) occurs causing loss of product ions
Solution Approach 1:
The ion trap system is divided into multiple rod sets (first rod set for trapping, second rod set for extraction) that can be independently controlled. This segmentation allows the trapping region to maintain conditions for product ion formation while the extraction region applies fields selectively for low m/z ion ejection without causing CID in the product ions.
Solution Approach 2:
Different regions of the ion trap system are given different functional properties: the first rod set maintains radial confinement for trapping precursor and product ions, while the second rod set is configured specifically for mass-selective extraction of low m/z ions. The DC potential gradient is applied locally between rod sets to achieve selective extraction without affecting the trapping region.
2Productivity
If conventional CID methods are used for protein fragmentation, then protein ions can be dissociated, but post-translational modifications are lost
Solution Approach 1:
The invention extracts low m/z product ions (including those containing post-translational modifications) from the reaction cell before they can be lost or degraded. By applying a DC potential gradient between the first and second rod sets, low m/z ions are selectively ejected while higher m/z precursor ions remain trapped for continued fragmentation reactions.
Solution Approach 2:
The system performs preliminary extraction of low m/z product ions during the fragmentation process itself, rather than after complete dissociation. This allows continuous removal of fragment ions containing post-translational modifications before secondary reactions or degradation can occur, preserving these important analytical features.
3Adaptability or versatility
If ExD methods are used for proteomics analysis, then post-translational modifications can be studied, but efficiency decreases due to secondary reactions
Solution Approach 1:
The system continuously extracts low m/z product ions from the reaction cell during the ExD process by maintaining a DC potential gradient between rod sets. This continuous extraction prevents product ions from remaining in the reaction region where they could undergo secondary reactions with reagent ions, thereby maintaining high dissociation efficiency while preserving product ion integrity for analysis.
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 enables efficient trapping and selective extraction of ions, maintaining precursor ions in the trap while extracting product ions, thereby preserving spectral integrity and reducing secondary reactions, improving the analysis of post-translational modifications in proteomics.
Implementation Method 1
applying an RF (radio frequency) potential to at least one of said rod sets to generate a radial trapping potential within at least the first rod set
Implementation Method 2
applying a DC potential (herein referred to as radial DC potential) to said first rod set to generate a radial DC field so as to modulate said radial RF trapping potential as a function of m/z of said ions
Implementation Method 3
applying a DC potential (herein referred to as axial DC potential) between said two rod sets to provide an axial bias potential between said two rod sets
Implementation Method 4
The DC bias potential can function as an extractive potential for first group of ions and as a barrier potential for a second group of ions having an opposite polarity relative to the first group
Data Source
AI summary
In a mass spectrometer, a method for trapping ions includes providing at least first and second multipole rod sets positioned in tandem, introducing a plurality of ions into the first rod set, applying an RF potential to at least one of said rod sets to generate a radial trapping potential within said rod sets, applying a radial DC potential to said first rod set so as to modulate said radial trapping potential set as a function of m/z of said ions, and applying a DC potential between said two rod sets to provide an axial bias potential between said two rod sets. The method can further comprise selecting an axial barrier potential to selectively extract ions having an m/z ratio less than a threshold from said first rod set into said second rod set.