Mass Spectrometer Ion Mobility Synchronization
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Solution Overview
Problem
Current mass spectrometry techniques face challenges in distinguishing multiply charged peptide precursor ions from singly charged background noise, leading to reduced sensitivity and inability to selectively target specific charge states, which hampers the identification of proteins in complex mixtures.
Innovation Solution
A method involving ion mobility spectrometry and mass filtering, where ions are temporally separated by their mobility and mass-to-charge ratio, allowing for the preferential transmission of multiply charged ions while attenuating singly charged ions, using a combination of ion mobility spectrometers and mass filters with variable cutoffs to enhance sensitivity and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If detector gain is lowered to reduce singly charged background noise, then sensitivity for detecting multiply charged ions is improved, but overall detection sensitivity is reduced
Solution Approach 1:
The invention segments the ion detection process by charge state using ion mobility spectrometry. Ions are first separated by mobility (which correlates with charge state), then the mass filter is dynamically adjusted to transmit only ions with mobility characteristics corresponding to multiply charged species. This segmentation allows the detector to operate at high gain while rejecting singly charged ions through the mobility-based pre-filtering and dynamic mass filtering, resolving the contradiction between noise reduction and sensitivity maintenance.
Solution Approach 2:
The invention performs preliminary separation of ions by mobility before mass analysis and detection. By pre-separating ions based on their mobility characteristics (which differ between singly and multiply charged ions), the system prepares the ion beam in advance to favor multiply charged ions. This preliminary action occurs upstream of the detector, allowing high detector gain to be used without being overwhelmed by singly charged background noise.
2Object-affected harmful factors
If discriminator voltage level is increased to favor multiply charged ions, then selectivity for multiply charged species is improved, but sensitivity is reduced
Solution Approach 1:
The invention dynamically changes the mass filter parameters (mass-to-charge ratio cutoff) in synchronisation with the ion mobility separation process. Instead of using a fixed high discriminator voltage that reduces sensitivity, the system adjusts the mass filter cutoff parameter over time to match the arrival times of ions separated by mobility. This dynamic parameter change allows selective transmission of multiply charged ions while maintaining high detector gain and sensitivity.
3Ease of operation
If conventional mass spectrometry is used to detect peptide precursor ions, then detection capability is provided, but singly charged background noise obscures multiply charged species
Solution Approach 1:
The invention introduces ion mobility spectrometry as an intermediary stage between the ion source and the mass spectrometer. This intermediary device separates ions based on mobility before they enter the mass analyzer, effectively filtering out singly charged background ions that would otherwise obscure multiply charged peptide precursor ions. The mobility-based intermediary preparation allows the conventional mass spectrometer to operate effectively without being overwhelmed by background noise.
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 increases sensitivity by allowing full detector gain operation and enables the selective transmission of desired charge states, improving the detection of multiply charged ions while reducing singly charged background noise, thereby enhancing the identification of proteins in mass spectrometry.
Implementation Method 1
temporally separating at least some of the ions according to their ion mobility in a first device
Implementation Method 2
mass filtering at least some of the ions according to their mass to charge ratio in a second device
Data Source
AI summary
A mass spectrometer is disclosed comprising an ion mobility spectrometer in combination with a quadrupole mass filter which is scanned in synchronization with the pulsing of ions into the ion mobility spectrometer thereby enabling ions having a particular charge state to be preferentially transmitted. Another embodiment replaces the quadrupole mass filter with an axial time of flight mass filter and an injection electrode.