Reflector TOF Mass Spectrometer for Small Molecule Imaging
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Solution Overview
Problem
Current mass spectrometric methods face challenges in achieving high sensitivity and spatial resolution for measuring small molecules (150-500 Daltons) due to interference from matrix ions and fragments, particularly in imaging mass spectrometry of thin tissue sections, where high scanning times and costs are associated with tandem time-of-flight mass spectrometers.
Innovation Solution
A time-of-flight mass spectrometer with a reflector is used to ionize analyte molecules, decompose them into daughter ions, and select these ions based on velocity for improved signal-to-noise ratio and spatial distribution analysis, employing metastable decay or collision-induced decomposition, allowing for high scanning frequencies and reduced electronic wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If tandem time-of-flight mass spectrometers are used to measure daughter ions for improved signal-to-noise ratio, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts only the essential function of daughter ion measurement from the complex tandem TOF system. By using a simple reflector TOF mass spectrometer with collision-induced dissociation, it isolates the critical measurement capability while eliminating the need for two separate mass analyzers, thereby reducing device complexity while maintaining measurement precision for small molecules
Solution Approach 2:
The patent creates a simplified copy of the tandem TOF functionality using a single reflector TOF instrument. Instead of implementing the full complex tandem system, it replicates the essential daughter ion detection capability through collision-induced dissociation combined with reflector TOF, achieving comparable measurement precision at lower cost and complexity
2Measurement precision
If high spatial resolution measurement grid spacing of 50 micrometers is used, then measurement precision is improved, but productivity decreases due to increased scanning time
Solution Approach 1:
The patent changes the key parameter of scanning speed by using a simple reflector TOF mass spectrometer that can rapidly acquire spectra. This parameter change enables high spatial resolution imaging at 50 micrometer grid spacing while maintaining practical productivity, as the simplified instrument can collect sufficient spectra faster than more complex systems
3Measurement precision
If multiple individual spectra are summed to achieve sufficient accuracy for concentration measurement, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent implements continuous rapid spectrum acquisition using the simple reflector TOF system. By continuously collecting spectra at high speed, it accumulates sufficient signal for accurate concentration measurement while minimizing total scanning time, as the continuous rapid acquisition allows fewer spectra to be summed compared to slower systems
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 achieves mass resolution and sensitivity comparable to tandem time-of-flight mass spectrometers while using lower-cost equipment, enabling rapid scanning of large areas with high spatial resolution and reduced measurement time, overcoming the limitations of earlier methods like PSD.
Implementation Method 1
ionization of the molecules by matrix-assisted laser desorption
Implementation Method 2
at least some of the molecular ions are made to decompose into daughter ions during their flight, for example, by metastable decay
Implementation Method 3
or by collisions with gas in a collision cell
Implementation Method 4
the molecular ions of interest and their daughter ions, having the same flight velocities, are selected by an ion selector which deflects all other ions
Implementation Method 5
one or a few selected species of daughter ion are deflected by the reflector onto the detector by a preset voltage at the reflector
Implementation Method 6
measured at the detector in the form of a short daughter ion spectrum
Data Source
AI summary
The invention relates to spatially resolved mass spectrometric measurement and visualization of the distribution of small molecules in a mass range from approximately 150 to 500 Daltons, for example drugs and their metabolites, in thin sections or other two-dimensional samples, preferably with ionization of the molecules by matrix-assisted laser desorption. The invention includes the steps measuring a daughter ion produced by forced decomposition of the molecular ion instead of the ionized analyte molecule itself, the daughter ion having a much better signal-to-noise ratio. The daughter ions are detected in a relatively simple reflector time-of-flight mass spectrometer instead of using an expensive time-of-flight tandem mass spectrometers for the measurement of the daughter ions. Advantageously, substantially faster and less expensive scanning of the thousands of mass spectra which serve as the basis for visualizing the spatial distribution of the analyte molecule is achieved, while the mass resolution and sensitivity are at least equally good.