Ion Mobility Spectrometry for Isomer Differentiation
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Solution Overview
Problem
Current mass spectrometry techniques, such as MS/MS, are limited in differentiating isomeric or isobaric compounds, like hydroxylated metabolites, as they produce identical spectra, making it difficult to determine the exact position of hydroxylation, and there is a lack of advancements in identifying small molecule structural isomers or isobars.
Innovation Solution
Combining ion mobility techniques with molecular modeling and theoretical collision cross-section calculations to identify sample compounds by measuring and comparing collision cross-section values using traveling wave ion mobility spectrometry, allowing for the differentiation of isomeric or isobaric species based on their physical size and shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If mass spectrometry (MS/MS) techniques are used to analyze compounds, then structural information can be obtained, but isomeric or isobaric species cannot be differentiated as they produce identical spectra
Solution Approach 1:
The patent combines ion mobility spectrometry with mass spectrometry to create a hybrid analytical system. The ion mobility dimension separates isomeric species based on their collision cross-sections before mass analysis, allowing differentiation of compounds that would otherwise produce identical MS/MS spectra. This merging of two analytical techniques resolves the information loss problem while maintaining measurement precision.
Solution Approach 2:
The patent introduces ion mobility as an additional separation dimension beyond traditional mass spectrometry. By measuring the drift time of ions through a buffer gas and calculating collision cross-sections, the system adds a new physical parameter for differentiation. This dimensional expansion allows distinction between isomeric species that have identical mass but different three-dimensional conformations.
2Productivity
If ion mobility techniques are used to separate isomeric species based on collision cross-section, then structural information is obtained rapidly, but the method requires combination with mass spectrometry for complete identification
Solution Approach 1:
The patent integrates ion mobility spectrometry and mass spectrometry into a unified analytical platform. The system sequentially performs ion mobility separation followed by mass spectrometry analysis, allowing rapid structural differentiation while maintaining comprehensive compound identification. This merged approach achieves fast separation without requiring separate analytical instruments.
Solution Approach 2:
The hybrid MS-IM system performs multiple functions within a single analytical workflow: it separates isomeric species by collision cross-section, identifies compounds by mass-to-charge ratio, and provides structural conformational information through drift time analysis. This multi-functionality reduces the need for multiple separate analytical techniques while maintaining high productivity.
3Measurement precision
If theoretical collision cross-section calculations are performed for multiple possible structures, then accurate identification is enabled, but computational time and resources increase
Solution Approach 1:
The patent performs theoretical collision cross-section calculations for all possible isomeric structures before experimental analysis. By pre-computing the collision cross-sections for each candidate structure and storing them in a reference database, the system eliminates the need for time-consuming calculations during actual compound identification. This preliminary action significantly reduces computational time during sample analysis while maintaining high identification accuracy through comparison with experimental measurements.
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 accurate identification of hydroxylated metabolites and other isomeric compounds without the need for additional structural characterization techniques like NMR or chemical standards, providing a rapid and efficient method for metabolite identification directly from biological matrices.
Implementation Method 1
Ion mobility (IM) has the ability to separate isomeric or isobaric species, such as hydroxylated metabolites, rapidly (msec) based on differences in their collision cross-section (Ω; physical size, and shape) in the gas-phase
Implementation Method 2
The ion mobility technique or cell preferably comprises a travelling wave ion mobility technique or cell
Data Source
AI summary
A method of and apparatus for identifying and/or characterising a sample that may incorporate two or more isomeric or isobaric compounds such as hydroxylated metabolites. The method involves modelling an ensemble of possible structures for each of two or more known isomeric or isobaric compounds, calculating a theoretical collision cross-section for each modelled structure, averaging the calculated values for each known compound to provide a theoretical collision cross-section value for each known compound. A travelling wave ion mobility cell is used to measuring a collision cross-section value for the sample compound and the measured value is then compared with the theoretical values to identify which of the two or more known compounds the sample compound most closely resembles.