Fourier Transform Mass Analyzer Ion Population Control
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Solution Overview
Problem
Fourier Transform mass analyzers face performance issues due to the interaction of ions with similar characteristic frequencies, leading to peak coalescence and frequency shifts, which complicates the separation and quantification of closely spaced ions, such as isotopologue species.
Innovation Solution
A method to adjust the target ion population in the mass analyzer by calculating an estimated frequency shift based on adjacent ion species' intensities and adjusting the ion population to maintain frequency shifts below a threshold, preventing peak coalescence, involving a first ion group analysis, calculation of adjusted target population, and subsequent mass analysis of a second ion group.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large ion population is accumulated in the FT mass analyzer to improve signal intensity, then the measurement sensitivity is improved, but the frequency shift between adjacent ions increases causing peak coalescence
Solution Approach 1:
The patent performs a preliminary mass analysis scan to measure the actual frequencies of adjacent ion species before the main measurement. Based on these preliminary measurements, it calculates the frequency shift and determines an adjusted ion population target that will keep the frequency shift below a threshold, thereby preventing peak coalescence in the subsequent main scan.
Solution Approach 2:
The patent dynamically adjusts the target ion population parameter based on the measured frequency shift between adjacent ions. By changing the ion population parameter adaptively rather than using a fixed value, it optimizes the balance between signal intensity and mass resolution, ensuring that peaks remain resolved while maintaining sufficient signal strength.
2Productivity
If the ion population is increased to reduce measurement time, then the productivity is improved, but the frequency interaction between ions causes peak coalescence
Solution Approach 1:
The patent implements a feedback mechanism where the results of a preliminary scan (frequency measurements of adjacent ions) are used to adjust the ion population target for the main scan. This feedback loop ensures that the ion population is optimized based on actual spectral conditions, maintaining reliable peak separation while achieving high productivity through efficient use of the FT mass analyzer.
3Manufacturing precision
If the target ion population is reduced to prevent peak coalescence, then the mass resolution is maintained, but the signal intensity decreases
Solution Approach 1:
The patent employs a dynamic approach where the target ion population is not fixed but adjusted based on the actual spectral conditions. By calculating the frequency shift from preliminary measurements and adaptively setting the ion population target, it achieves the minimum necessary ion population to maintain resolution while maximizing signal intensity, rather than using a conservative fixed low population.
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 prevents peak coalescence and maintains accurate separation of closely spaced ions by controlling frequency shifts, ensuring reliable identification and quantification of ion species.
Implementation Method 1
FT mass analyzers utilize electric or electromagnetic fields to confine ions to a trapping region, where the ions undergo periodic motion having frequencies characteristic of their mass-to-charge ratios (m/z's)
Implementation Method 2
the ions undergo periodic motion having frequencies characteristic of their mass-to-charge ratios (m/z's)
Implementation Method 3
A detector is utilized to measure a time-varying signal, referred to as a transient, generated by the motion of the trapped ions, and the transient is subsequently processed by performing a Fourier transform to convert it to the frequency space
Implementation Method 4
the interaction of two adjacent ions (ions of closely spaced mass-to-charge ratios (m/z's)) results in a shift of both of their frequencies towards the other
Data Source
AI summary
A method is disclosed for operating a mass spectrometer having a Fourier Transform (FT) analyzer, such as an orbital electrostatic trap mass analyzer, to avoid peak coalescence and/or other phenomena arising from frequency-shifting caused by ion-ion interactions. Ions of a first group are mass analyzed, for example in a quadrupole ion trap analyzer, to generate a mass spectrum. The estimated frequency shift of the characteristic periodic motion in the FT analyzer is calculated for one or more ion species of interest based on the intensities of adjacent (closely m/z-spaced) ion species. If the estimated frequency shift(s) for the one or more ion species exceeds a threshold, then a target ion population for an FT analyzer scan is adjusted downwardly to a value that produces a shift of acceptable value. An analytical scan of a second ion group is performed at the adjusted target ion population.