Ion Mobility-Tandem Mass Spectrometer Lipid Structure Determination
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Solution Overview
Problem
Existing methods for determining the chemical structure of lipids, particularly in identifying the position of carbon-carbon double bonds and sn-positions, face challenges such as low abundance of diagnostic ions, poor duty cycle, and limited resolution, especially when analyzing complex biological samples.
Innovation Solution
A method involving ionization, ion mobility-based separation, selective dissociation, and tandem mass spectrometry is employed. This method includes a first dissociation step to break a weaker chemical bond, followed by mass-based selection and a second dissociation step to generate diagnostic ions, thereby improving ion abundance and spectral resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pseudo MS3 or MS3 analysis methods are used to identify sn-position and double bond position, then structural identification capability is improved, but diagnostic ion abundance is insufficient and duty cycle is low
Solution Approach 1:
The patent segments the tandem mass spectrometry process into distinct stages: first CID to generate precursor ions, then ion mobility separation to isolate specific ion populations, followed by second CID to generate diagnostic ions. This segmentation allows each stage to be optimized independently, improving overall diagnostic ion abundance while maintaining structural identification capability
Solution Approach 2:
Ion mobility spectrometry acts as an intermediary between the first and second CID stages. It separates ions based on their mobility in the gas phase, enabling selective enrichment of specific ion populations before the second dissociation stage, thereby increasing diagnostic ion abundance without sacrificing measurement precision
2Measurement precision
If quadrupole is used to select target ions, then specific ion selection is achieved, but non target ions are lost and overall duty cycle is low
Solution Approach 1:
The patent adds ion mobility as an additional dimension for ion selection beyond the traditional mass-to-charge ratio selection by quadrupole. This extra dimension enables more precise ion isolation while maintaining higher ion transmission, thereby improving duty cycle without sacrificing selection specificity
3Measurement precision
If ion trap mass spectrometer is used for charge-tagging derivatization and MS3 analysis, then C═C position and sn-position identification is achieved, but duty cycle and resolution are limited
Solution Approach 1:
The patent merges ion mobility spectrometry with tandem mass spectrometry in a hybrid instrument configuration. This combination allows the system to achieve both high duty cycle (from the linear ion trap's continuous ion accumulation capability) and high resolution (from ion mobility separation), overcoming the limitations of using ion trap alone for MS3 analysis
4Measurement precision
If ion mobility spectrometry is used for isomer separation, then separation resolution is improved, but diagnostic ion abundance for structural identification remains insufficient
Solution Approach 1:
The patent performs preliminary collision-induced dissociation before ion mobility separation to generate fragment ions that will serve as diagnostic ions. This preliminary action ensures that sufficient diagnostic ion abundance is available after the ion mobility separation stage, while still achieving high isomer separation resolution
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
The proposed method enhances the signal intensity of diagnostic ions, simplifies the mass spectrum, and improves the analysis throughput, enabling more precise determination of lipid structures, including the position of carbon-carbon double bonds and sn-positions, in a single injection.
Implementation Method 1
an ionization step of ionizing a sample to obtain sample ions
Implementation Method 2
an ion mobility-based separation step of separating target lipid ions from the sample ions based on ion mobility
Implementation Method 3
a first dissociation step of dissociating the target lipid ions with dissociation energy adjusted to break a first chemical bond of the target lipid ions
Implementation Method 4
a mass-based selection step of selecting the target lipid ions, whose first chemical bond is broken, based on a mass number to obtain fragment ions
Implementation Method 5
a second dissociation step of dissociating the fragment ions to at least break a second chemical bond of the fragment ions which has bond energy higher than the first chemical bond, to obtain diagnostic ions
Implementation Method 6
a mass analysis step of performing a mass analysis on the diagnostic ions
Data Source
AI summary
The present disclosure relates to the field of mass spectrometry, and particularly provides a method for determining a chemical structure of a lipid and an ion mobility-tandem mass spectrometer. The method for determining a chemical structure of a lipid includes: an ionization step of ionizing a sample to obtain sample ions; an ion mobility-based separation step of separating target lipid ions from the sample ions based on ion mobility; a first dissociation step of dissociating the target lipid ions with dissociation energy adjusted to break a first chemical bond of the target lipid ions; a mass-based selection step of selecting the target lipid ions, whose first chemical bond is broken, based on a mass number to obtain fragment ions; a second dissociation step of dissociating the fragment ions to at least break a second chemical bond of the fragment ions which has bond energy higher than the first chemical bond, to obtain diagnostic ions; and a mass analysis step of performing a mass analysis on the diagnostic ions.