Ion Mobility Mass Filtering for Slow Analyzer Time Resolution
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Solution Overview
Problem
The integration of 'slow' mass analyzers with high-resolution ion mobility separators (hrIMS) in mass spectrometry leads to a time mismatch, causing ion packets to be detected in the same spectrum, which degrades the separation achieved with ion mobility, especially in proteomics and metabolomics workflows.
Innovation Solution
The method involves operating an analytical instrument with an ion mobility separator, a mass filter, and a mass analyzer, where the mass filter scans the center m/z of its isolation window and controls its width to transmit ions within a specific ion mobility arrival time range, ensuring that ions are analyzed in a manner compatible with the time resolution of the mass analyzer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a slow mass analyser is used to achieve high mass resolution, then measurement precision is improved, but the time resolution of the ion mobility separator deteriorates
Solution Approach 1:
The patent segments the ion mobility separation process into multiple discrete time bins within each TIMS scan. By dividing the continuous ion mobility separation into N time bins, the system can assign ions to specific mass analysis scans based on their arrival time, effectively decoupling the long mass analysis duration from the ion mobility time resolution requirement.
Solution Approach 2:
The patent performs preliminary ion mobility separation and time binning before mass analysis. Ions are separated by ion mobility in the TIMS device first, then assigned to different time bins based on their arrival time. This preliminary sorting allows the slow mass analyser to process ions in an organized sequence without compromising the effective time resolution of the ion mobility separation.
2Measurement precision
If multiple time bins are used to improve ion mobility resolution, then measurement precision is improved, but the number of mass analysis scans required increases
Solution Approach 1:
The patent makes the mass analyser perform multiple functions by having it analyze ions from different charge states and different time bins in alternating scans. The same mass analyser that analyzes singly charged ions in one scan can analyze doubly charged ions in the next scan, eliminating the need for separate dedicated analysers for different ion types and maintaining high throughput.
Solution Approach 2:
The patent implements periodic scanning where the mass analyser alternates between analyzing ions from different charge states in a systematic pattern. This periodic action allows complete coverage of the ion mobility-m/z space over multiple cycles while maintaining efficient use of the mass analyser, achieving both high resolution and acceptable throughput.
3Measurement precision
If the mass analyser scan duration is increased to achieve high resolution, then measurement precision is improved, but the compatibility with ion mobility separation deteriorates
Solution Approach 1:
The patent adds the time bin dimension to the traditional mass analysis, creating a two-dimensional data structure (time bin vs. m/z). This dimensional change allows the system to preserve both the high mass resolution from long scan durations and the ion mobility separation quality, as ions are now organized in a 2D space that captures both separation dimensions independently.
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 enhances the resolution of ion mobility separation while maintaining the throughput and depth of analysis, even with 'slow' mass analyzers, by optimizing the control of the quadrupole mass filter to match mass selection with the required mobility time resolution.
Implementation Method 1
an ion mobility separator arranged downstream of the ion source and configured to separate received ions according to their ion mobility
Implementation Method 2
a mass filter arranged downstream of the ion mobility separator and configured to filter received ions according to their mass to charge ratio (m/z)
Implementation Method 3
a mass analyser arranged downstream of the mass filter and configured to determine the mass to charge ratio of received ions
Data Source
AI summary
An analytical instrument comprises an ion mobility separator, a mass filter downstream of the ion mobility separator, and a mass analyser downstream of the mass filter. The ion mobility separator performs ion mobility separation scans to separate ions according to ion mobility. The mass filter filters the separated ions using an isolation window, and during each scan: (i) scanning a centre mass to charge ratio (m/z) of the isolation window, and (ii) controlling a width Δmz of the isolation window such that ions emerging from the ion mobility separator within an ion mobility arrival time range ΔT are transmitted by the mass filter. The mass analyser performs mass analysis scan(s) during each ion mobility separation scan in which the mass analyser analyses ions transmitted by or derived from ions transmitted by the mass filter, each mass analysis scan having a duration T, and wherein ΔT<T.