Precursor Charge-State Prediction Using Ion Mobility Ionograms
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Solution Overview
Problem
Mass spectrometry techniques face challenges in determining the charge state of precursor ions due to peak overlapping issues, where singly charged ions with a certain mass can have the same mass-to-charge ratio as doubly charged ions with double the mass, leading to interference and complexity in identifying and quantifying molecules, especially in complex sample analyses.
Innovation Solution
A method and system that determine the charge state of precursor ions by analyzing product ions, using ion-mobility devices and tandem mass spectrometry to generate ionograms with compensation voltage and intensity axes, identifying peak characteristics such as peak width and voltage values to infer the charge state of precursor ions, and filtering ions based on mass and mobility to reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mass spectrometry measures mass-to-charge ratio (m/z) for detected ions, then mass analysis can be performed, but peak overlapping occurs where singly charged ions with mass M and doubly charged ions with mass 2M appear at the same m/z value
Solution Approach 1:
The patent introduces ion mobility separation as an additional dimension beyond mass-to-charge ratio. Ions are separated based on their mobility in a gas phase under electric fields, which depends on their size, shape, and charge. This creates a two-dimensional separation space (mobility × m/z) that resolves the peak overlapping problem, as ions with different charge states have different mobility characteristics even when they share the same m/z value.
Solution Approach 2:
The patent segments the complex mixture of ions into distinct groups based on their ion mobility characteristics. By applying compensation voltage in differential mobility spectrometry, ions are separated into discrete mobility clusters, effectively segmenting the overlapping peaks into resolvable components. This segmentation allows individual charge state determination for each ion group.
2Measurement precision
If multiple compensation voltage values are applied to separate precursor ions by mobility, then charge state determination accuracy improves, but analysis time increases
Solution Approach 1:
The patent applies periodic scanning of compensation voltage values to achieve ion separation. By systematically varying the compensation voltage across a range of values and acquiring spectra at each step, the method periodically sweeps through different mobility selections. This periodic action allows comprehensive charge state determination while optimizing the balance between accuracy and analysis time through efficient voltage stepping.
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 accuracy and speed of database searches by correctly identifying and grouping precursor ions, reducing the complexity of peak overlapping and improving the confidence of results in mass spectrometry analyses, particularly in LC-MS/MS experiments.
Implementation Method 1
selecting a group of precursor ions from the received sample ions based on mobility
Implementation Method 2
fragmenting, by a fragmentation device, the group of precursor ions to produce a group of product ions
Implementation Method 3
performing a tandem mass spectrometry analysis on the group of product ions to generate an intensity and mass-to-charge ratio (m/z)
Data Source
AI summary
A method for improved mass spectrometry by determining charge state of precursor ions from an analysis of product ions, includes receiving sample ions. A group of precursor ions is selected from the received sample ions based on mobility. A fragmentation device fragments the group of precursor ions to produce a group of product ions. A tandem mass spectrometry analysis is performed on the group of product ions to generate an intensity and mass-to-charge ratio (m/z) of the group of product ions. An ionogram is generated, based on the generated intensities and mass, to charge ratios for the groups of product ions generated for each of the mobility selection. The ionogram includes a first axis representing compensation voltage value and another axis representing intensity. A product ion peak is identified in the ionogram. At least one peak characteristic is identified of the product ion peak. A charge state of a precursor ion that was fragmented to form the product ions represented in the product ion peak is determined based on the at least one peak characteristic of the produce ion peak.