Static Wien Filter Tuning for Isotope Interference Rejection
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Solution Overview
Problem
Existing mass spectrometers face challenges in accurately resolving isotopes with marginal mass differences, particularly in multicollector inductively coupled plasma mass spectrometers (MC-ICP-MS), due to isotopic interferences that require complex chemical cleaning steps and limit analysis to high-quantity samples.
Innovation Solution
A method involving a mass spectrometer with a static field mass filter comprising a combination of two Wien filters, which uses a pre-mass-filter with a bandpass characteristic to separate ions, reducing interference and optimizing electric and magnetic field settings for improved resolution and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pre-filter comprising a combination of two Wien filters is used to block the intense Ar beam, then the total ion load is greatly reduced and abundance sensitivity is improved, but optimizing the settings of the pre-filter is not intuitive and device complexity increases
Solution Approach 1:
The patent implements an automated feedback control system that scans the electric field strength of the Wien filters and uses a detector to monitor ion transmission. The system automatically identifies the optimal field strength range where the Ar beam is blocked while maintaining transmission of analyte ions, eliminating the need for manual optimization and making the complex tuning process intuitive.
Solution Approach 2:
The system performs self-optimization by automatically scanning and determining the optimal electric field settings for the Wien filters based on detected ion signals. This self-service capability allows the pre-filter to automatically adapt to different measurement conditions without requiring expert intervention for tuning.
2Measurement precision
If a collision reaction cell is used to mass-shift analyte ions by reacting with reactive gas, then mass resolution of interfering ions is improved, but device complexity and measurement time increase
Solution Approach 1:
The patent applies preliminary mass filtering using the Wien filter pre-filter before ions enter the collision reaction cell. By pre-selecting ions based on their mass-to-charge ratio and blocking the intense Ar beam early in the ion path, the system reduces the ion load entering the collision cell, thereby simplifying the subsequent chemical cleaning process and reducing measurement time.
3Measurement precision
If the electric field strength of Wien filters is increased to improve mass filtering, then interfering ions are blocked more effectively, but transmission of analyte ions decreases
Solution Approach 1:
The patent implements dynamic field strength scanning where the electric field of the Wien filters is varied over time to sweep through different transmission windows. This dynamic approach allows the system to temporarily optimize for blocking interfering ions during scanning, then settle on an optimal field strength that balances interference rejection with analyte ion transmission, maximizing both precision and 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 enables more reproducible tuning and better measurement results by effectively blocking unwanted ions, such as Argon, and enhancing the resolving power and abundance sensitivity of the instrument.
Implementation Method 1
a static field mass filter having a first Wien filter and a second Wien filter
Implementation Method 2
setting the one of the electric field or the magnetic field of the first and second Wien filters
Implementation Method 3
setting the one of the electric field or the magnetic field of the first and second Wien filters
Implementation Method 4
the analyte ions are mass-shifted (by forming molecules when reacting with the gas), while the interfering ions are not
Data Source
AI summary
A method of analysing a field of a mass spectrometer comprising a mass analyser and a static field mass filter having a first Wien filter and a second Wien filter is provided. The method includes, for each of a plurality of predetermined strengths of one of an electric field or a magnetic field of the first and second Wien filters: setting the one of the electric field or the magnetic field of the first and second Wien filters to the predetermined strength; causing a beam of ions comprising one or more ion species to be injected through the static field mass filter; and measuring, using the mass analyser, a respective intensity of ions of each of the one or more ion species in the beam.