Static Field Mass Filter Response for Isotope Interference Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing mass spectrometers struggle to accurately resolve isotopes with marginal mass differences, requiring complex chemical cleaning steps and limiting analysis to high-quantity samples due to interference from isotopes like 87Sr and 87Rb, which cannot be easily mass-resolved with commercially available instruments.
Innovation Solution
Implementing a pre-mass-filter with a combination of two Wien filters to block interfering ions and a collision reaction cell to mass-shift analyte ions, allowing for improved resolution and reduced ion load, combined with a method to optimize the bandpass characteristic of the pre-filter using interpolations and interpolant functions.
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 resolving power is improved, but optimising the settings of the pre-filter is not intuitive and complex
Solution Approach 1:
The patent implements an automated feedback system where a computer program controls the pre-filter settings based on real-time monitoring of ion beam characteristics. The system automatically adjusts the Wien filter parameters to optimize blocking of interfering ions while maintaining transmission of analyte ions, eliminating the need for manual trial-and-error optimization.
Solution Approach 2:
The mass spectrometer system performs self-optimization of the pre-filter settings through automated control algorithms. The computer program independently determines optimal filter parameters based on measured ion intensities and mass spectral data, allowing the instrument to self-adjust without requiring expert user intervention or intuitive knowledge of filter characteristics.
2Measurement precision
If complex chemical cleaning steps are used to remove interfering ions, then isotope ratio determination accuracy is improved, but the analysis becomes time consuming and limited to high-quantity samples
Solution Approach 1:
The patent replaces mechanical/chemical separation methods with a physical field-based separation approach. Instead of using complex chemical cleaning steps to remove interfering ions, the system uses a pre-filter comprising Wien filters that employ crossed electric and magnetic fields to physically separate and block interfering ions based on their mass-to-charge ratio, allowing direct measurement without time-consuming chemical preparation.
Solution Approach 2:
The patent changes the separation parameter from chemical properties to physical field interactions. By adjusting the electric and magnetic field strengths in the Wien filters, the system dynamically optimizes the mass-to-charge ratio window for transmission, enabling efficient separation of interfering ions from analyte ions based on their different trajectories in the crossed fields, thus eliminating the need for chemical cleaning.
3Measurement precision
If the mass difference between sample ions and interfering ions is marginal, then the ions cannot be easily resolved by the mass spectrometer, but using a collision reaction cell to mass-shift analyte ions makes the mass difference large enough to be easily resolved
Solution Approach 1:
The patent applies preliminary mass filtering before the ions enter the collision reaction cell. The pre-filter comprising Wien filters selectively transmits ions within a specific mass-to-charge ratio window, pre-separating analyte ions from interfering ions based on their mass differences. This preliminary action reduces the burden on the collision reaction cell and downstream mass analyzer, improving overall resolution efficiency.
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
Enhances the resolving power and abundance sensitivity of mass spectrometers by effectively separating target ions from interferences, reducing the need for complex chemical cleaning and enabling analysis of lower-quantity samples.
Implementation Method 1
a pre-mass-filter with a bandpass characteristic can be used, such that only the masses of interest reach the collision cell while ions that interfere with the mass shifted ions are not transmitted. In EP 3 769 334 B1, the entire contents of which are herewith incorporated by reference in this document, a pre-filter comprising a combination of two Wien filters is disclosed.
Implementation Method 2
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), while the interfering ions are not. For example, the analyte ions become 16 atomic mass units (amu) heavier when reacting with oxygen
Data Source
AI summary
A method of determining an expected response to injecting a beam of ions of a species of interest into a static field mass filter of a mass spectrometer including a mass analyser is provided. The method includes: measuring an intensity of ions injected into the static field mass filter for various combinations of test ion species, test magnetic field strengths, and test electric field strengths; determining electric field strengths corresponding to an intensity equal to a first and a second fraction of the measured peak intensity; based on a predetermined relationship between magnetic field strength, electric field strength and centre mass of the static field mass filter, determining mass values corresponding to the determined electric field strengths; and interpolating, from said mass values and for each ion species and for at least one of the test magnetic field strengths, expected mass values for an ion species of interest.