Gated DC Voltage Deflects Ions in FT-ICR Mass Spectrometers
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Solution Overview
Problem
Existing methods for introducing ions into a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) often result in large magnetron orbits, which complicate cyclotron excitation and detection, leading to distorted mass spectra and potential ion loss due to improper ion injection and asymmetric electric fields.
Innovation Solution
A method involving gated DC voltages applied to the mantle electrodes of the ICR cell to deflect ions radially, reducing their magnetron orbits before cyclotron excitation, and adjusting these voltages to minimize even-numbered harmonic peak intensities, thereby controlling ion motion and improving spectral resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ions are introduced into the ICR cell using conventional methods, then ion capture is achieved, but large magnetron orbits are generated which complicate cyclotron excitation and detection
Solution Approach 1:
A DC voltage is applied to the mantle electrode before ion injection to pre-establish an asymmetric electric field. This preliminary action creates favorable conditions for ion capture by reducing the initial magnetron orbit radius, thereby preventing the formation of large magnetron orbits that would complicate subsequent cyclotron excitation and detection.
Solution Approach 2:
The asymmetric electric field generated by the DC voltage on the mantle electrode acts as a preliminary counter-action to the symmetric trapping field. By introducing this opposing field component before ion injection, the method counteracts the formation of large magnetron orbits, thereby preventing measurement inaccuracies before they occur.
2Reliability
If symmetric trapping fields are used to confine ions, then ion confinement is achieved, but even-numbered harmonic peaks appear in the spectrum due to large magnetron orbits
Solution Approach 1:
A DC voltage is applied to the mantle electrode to create an asymmetric electric field component in the radial direction. This asymmetry counteracts the symmetric trapping field's tendency to produce large magnetron orbits, thereby eliminating even-numbered harmonic peaks and spectral distortion while maintaining effective ion confinement.
3Productivity
If fast pre-separation techniques like liquid chromatography are used, then analysis speed is improved, but ion injection timing becomes critical to avoid large magnetron orbits
Solution Approach 1:
The DC voltage is applied to the mantle electrode in advance of ion injection, creating the asymmetric electric field condition before ions enter the cell. This preliminary preparation simplifies the operation of fast pre-separation techniques by eliminating the need for precise timing control during ion injection, thereby maintaining high analysis speed while improving ease of operation.
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 effectively reduces magnetron orbits, enhancing the accuracy of mass spectra by minimizing even-numbered harmonic peaks and allowing for more efficient ion capture and detection, even in fast pre-separation techniques like liquid chromatography.
Implementation Method 1
A DC voltage is applied to a mantle electrode of the ICR cell prior to a cyclotron excitation of injected ions such that injected ions are deflected inside the FT-ICR cell in a radial direction to a smaller magnetron orbit after their entrance in the ICR cell
Implementation Method 2
In a magnetic field with the flux density B, an ion with the mass m, the elementary charge e and the charge number z performs a circular motion (cyclotron motion) in the radial plane perpendicular to the magnetic field lines
Implementation Method 3
The cylinder mantle electrodes of such a simple ICR cell are grounded, thus, an electric trapping field is formed in the ICR cell between the end electrodes and the cylinder mantle
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
The invention relates to a method and a device for introducing ions into an ICR cell of Fourier transform ion cyclotron resonance mass spectrometers, in particular with a reduced the magnetron orbit. The invention is based on applying at least one gated DC voltage to a mantle electrode of the ICR cell prior to the excitation of the cyclotron motion such that injected ions are deflected inside the ICR cell in at least one radial direction.