Quadrupolar 2ω-Detection Phase Shift for Harmonic Suppression
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Solution Overview
Problem
In ion cyclotron resonance mass spectrometry, especially in broad band operations, 1ν-subharmonic signals complicate the interpretation of spectra due to their high abundance and stability issues, which current methods only partially address, limiting mass resolution and accuracy in complex mixture analyses.
Innovation Solution
A method involving quadrupolar 2ω-detection with two bunches of ions excited using phases differing by 180°, where the transients are added together to significantly reduce 1ν-subharmonic signals, and applying this principle to multiple electrode nω-detection to suppress subharmonic and harmonic signals and their sidebands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If quadrupolar 2ω-detection is used to improve mass resolution, then mass resolution is improved, but 1ν-subharmonic signals appear at high abundance complicating spectrum interpretation
Solution Approach 1:
The patent applies asymmetry by introducing a phase shift of approximately 180° between two excitation waves applied to different bunches of ions. This asymmetric phase relationship causes the subharmonic signals to oscillate out of phase, enabling their cancellation when transients are added together, while the fundamental signals remain in phase and constructively interfere
Solution Approach 2:
The patent employs periodic action by performing multiple transient measurements with alternating excitation phases and then combining them. The periodic alternation of phase states (0° and 180°) allows systematic cancellation of unwanted subharmonic components while preserving the desired fundamental signals through constructive interference
2Adaptability or versatility
If broad band operation is used to analyze complex mixtures, then analytical coverage is improved, but harmonic signals complicate spectrum interpretation
Solution Approach 1:
The phase asymmetry technique suppresses both subharmonic and harmonic signals simultaneously, enabling clean broad band spectra that maintain high analytical coverage for complex mixture analysis without interference from unwanted signal components
Solution Approach 2:
The method extracts and removes unwanted harmonic and subharmonic components from the spectrum by selective cancellation through phase-modulated transient addition, leaving only the desired fundamental ion signals for interpretation
3Illumination intensity
If offset magnetron orbits are present, then ion signal intensity increases in dipolar 1ω-detection, but even-numbered harmonics and sidebands become more abundant
Solution Approach 1:
The 180° phase shift creates asymmetric excitation conditions that cause even-numbered harmonics generated by offset magnetron orbits to cancel out during transient addition, while the fundamental ion signal remains robust
Solution Approach 2:
By periodically alternating the excitation phase between 0° and 180° for different ion bunches and combining the resulting transients, the method systematically eliminates even-numbered harmonics while preserving the fundamental signal intensity
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 1ν-subharmonic signals by a factor of ten, enhancing the interpretability of mass spectra and achieving higher mass resolution and accuracy by eliminating or minimizing subharmonic and harmonic peaks, thereby improving the evaluation of transients.
Implementation Method 1
excitation of ions in an ICR cell with an excitation wave to a frequency ν+
Implementation Method 2
the axis of the ionic magnetron orbit in a cylindrical ICR cell shows a radial offset from the geometric axis of the cell
Implementation Method 3
detecting only ion species in a mass (m/z) range around a single Dalton
Implementation Method 4
transforming the sum of the first and second transients into a frequency spectrum (or a mass spectrum or m/z spectrum)
Data Source
AI summary
The invention relates to reducing harmonic signals in FT-ICR spectra. Since harmonic signals in quadrupolar 2ω-detection can be more abundant for the same ion motion in the ICR cell as compared to harmonic signals in classical dipolar 1ω-detection, they could hitherto not be reduced to satisfactory levels by any known method, such as gated deflection during ion introduction into, and correcting for an offset electric field axis in the ICR cell. The present disclosure foresees, in addition to other methods carried out for improving the measurement conditions as the case may be, performing the quadrupolar 2ω-detection at least twice, where the phase of the ion excitation radio frequency is turned by 180° in the second measurement. From the sum transient, a Fourier-transformed spectrum is derived. As a result, the broad band spectra of complex substance mixtures like crude oil become cleaner, and misinterpretations of false (harmonic) peaks are minimized.