Dual Wien Filter Field Analysis for Isotope Interference Separation
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Solution Overview
Problem
Multicollector mass spectrometers face challenges in accurately resolving isotopic ratios due to isotopic interferences, requiring complex chemical cleaning steps and limiting analysis to high-quantity samples, especially for elements like 87Sr which cannot be easily distinguished from 87Rb.
Innovation Solution
A method involving a static field mass filter with a combination of two Wien filters and a collision reaction cell is used to mass-shift analyte ions, allowing for improved resolution and separation of interfering ions, while a pre-mass-filter with a bandpass characteristic ensures only relevant masses reach the collision cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a collision reaction cell is used to mass-shift analyte ions, then the resolving power improves, but the device complexity increases
Solution Approach 1:
A collision reaction cell filled with reactive gas serves as an intermediary component between the ion source and mass analyzer. The reactive gas mediates the mass-shifting process by causing analyte ions to form molecular ions, thereby separating their mass from interfering ions without requiring direct modification of the main mass analyzer structure.
Solution Approach 2:
The mass spectrometer is segmented into distinct functional modules: ion source, collision reaction cell, pre-mass-filter, and mass analyzer. This segmentation allows each component to perform its specific function independently, with the collision cell handling mass-shifting and the pre-mass-filter handling interference removal, thereby improving overall resolving power while managing complexity through modular design.
2Measurement precision
If a pre-mass-filter with bandpass characteristic is used to block interfering ions, then the measurement accuracy improves, but the device complexity increases
Solution Approach 1:
A pre-mass-filter is placed before the main mass analyzer to perform preliminary filtering of interfering ions. This preliminary action removes unwanted ions before they reach the collision cell and mass analyzer, improving measurement accuracy by preventing interference with the mass-shifting process and subsequent detection.
Solution Approach 2:
The pre-mass-filter acts as an intermediary filtering stage that selectively transmits ions of interest while blocking interfering ions. This intermediary component simplifies the workload of the main mass analyzer by pre-processing the ion beam, thereby improving measurement accuracy without requiring the main analyzer to handle all interference removal.
3Measurement precision
If the Ar beam is blocked early in the ion optics, then the abundance sensitivity improves, but the device complexity increases
Solution Approach 1:
The intense Ar beam caused by the plasma source is extracted and blocked early in the ion optics path, before ions enter the collision reaction cell. This extraction of the harmful Ar beam prevents it from overwhelming the detector and improves abundance sensitivity by reducing the total ion load that reaches the sensitive detection stages.
4Measurement precision
If complex chemical cleaning steps are used to remove isotopic interferences, then the measurement accuracy improves, but the productivity decreases
Solution Approach 1:
Complex chemical cleaning steps are replaced by a physical mass-shifting mechanism using a collision reaction cell. Instead of chemically processing samples to remove interferences, the system uses controlled collisions with reactive gas to physically shift the mass of analyte ions, thereby eliminating the need for time-consuming chemical preparation while maintaining measurement accuracy.
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 enhances the resolving power and abundance sensitivity of the mass spectrometer, reducing ion load and improving measurement accuracy by optimizing the electric and magnetic field settings of the Wien filters, leading to more reproducible tuning and better measurement results.
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 ions are guided through a cell which is filled with a reactive gas. With an appropriate choice of the gas, one can obtain that the analyte ions are mass-shifted (by forming molecules when reacting with the gas)
Data Source
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Figure 2B
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 comprises, 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.