FT-ICR Cell Electric Field Correction via Mantle Electrode Voltage
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Solution Overview
Problem
Asymmetric electric fields in Fourier transform ion cyclotron resonance mass spectrometers (FT-ICR MS) lead to distorted cyclotron orbits and reduced measurement accuracy due to radial components of the trapping field, causing ions to escape and resulting in inaccurate mass spectrometry.
Innovation Solution
A method involving the adjustment of DC voltages on mantle electrodes to correct asymmetric electric fields by monitoring ion signals at specific frequencies and adjusting voltages to minimize satellite peaks, thereby aligning the electric field axis with the cell axis, ensuring symmetric ion motion and accurate detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electric trapping field is applied to prevent ions from escaping the cell axially, then ion containment is improved, but asymmetric electric fields cause radial distortion of cyclotron orbits and reduced measurement accuracy
Solution Approach 1:
The patent applies different DC voltages to different mantle electrodes to create localized field corrections. Specifically, at least one mantle electrode is supplied with an individually adjustable DC voltage to correct asymmetric electric fields in specific regions of the cell, while maintaining the overall trapping field for ion containment.
Solution Approach 2:
The patent changes the DC voltage parameter of mantle electrodes to correct field asymmetries. By adjusting the DC voltage supplied to at least one mantle electrode, the electric field distribution is modified to reduce radial distortion of ion orbits while preserving axial trapping.
2Measurement precision
If DC voltages are adjusted to correct electric field asymmetry, then measurement accuracy is improved, but device complexity increases due to additional voltage control requirements
Solution Approach 1:
The patent segments the mantle electrodes into groups where at least one electrode can be independently voltage-controlled. This segmentation allows targeted correction of field asymmetries without requiring complete redesign of the electrode structure, balancing complexity and performance.
Solution Approach 2:
The mantle electrodes serve multiple functions: they provide the trapping field for axial ion confinement and simultaneously enable field asymmetry correction through individual DC voltage adjustment. This multi-functionality reduces the need for separate correction electrodes, limiting complexity increase.
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 the intensity of satellite peaks and harmonics, minimizing ion loss and improving the accuracy of mass spectrometry by ensuring ions follow central, small magnetron orbits, enhancing the reliability of FT-ICR MS measurements.
Implementation Method 1
the cyclotron motion of the ions is excited by an oscillating (RF) electric field with a scanned frequency (Chirp). When the frequency of the scanned oscillating field becomes equal to the cyclotron frequency of an ion with mass m and charge number z, its cyclotron motion gets resonantly excited.
Implementation Method 2
Coherently moving ions in this excited cloud induce image charges of the same magnitude at the detection electrodes that oscillate with the same frequency and with the same phase. Such oscillating image charges (image currents) generated by all excited ion clouds are recorded
Implementation Method 3
To prevent the ions from escaping in the axial direction, an electric trapping field is required. Therefore, axially, at both ends of the cell, end electrodes (or end plates) are placed to which a relatively low DC voltage is applied, normally 1-2 volts.
Implementation Method 4
The cyclotron radius rc of an ion with the mass m, the elementary charge e, the charge number z, and the kinetic energy Ekin in a magnetic field of the flux density B is given by the following equation: The magnetic field can only trap ions in the plane perpendicular to the magnetic field lines so that they cannot radially escape the cell.
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
The invention relates to a method and a device for optimization of electric fields in measurement cells of Fourier transform ion cyclotron resonance mass spectrometers. The invention is based on the rationale that asymmetric electric fields with uniformly or nonuniformly perturbed field axes can appear in ion cyclotron resonance cells and therefore the axis of the magnetron orbit can become radially displaced. Shifted magnetron orbits negatively affect the cyclotron excitation, deteriorate the FT-ICR signal, increase the intensity of an even-numbered harmonics peak, lead to stronger side bands of the FT-ICR signal, and in extreme cases, cause loss of ions. The present invention helps in probing the shift of the magnetron motion, detecting parameters indicative of the offset of the electric field axis and/or correcting it by trimming it back to the geometric axis of the cell.