Variable Energy Electron Ionization Source for Mass Spectrometry
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Solution Overview
Problem
Conventional electron ionization (EI) methods in mass spectrometry typically use a constant electron energy of 70 eV, which is not optimal for all compounds, leading to reduced formation of higher mass ions essential for chemical identification, and require switching to soft ionization techniques at lower energies, increasing cost and complexity.
Innovation Solution
An EI source capable of operating over a range of electron energies, allowing for the adjustment of electron energy to optimize the formation of molecular and high mass ions by producing an electron beam at varying energies, such as 10 eV to 150 eV, and switching between hard and soft ionization modes during a single experiment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional EI uses constant 70 eV electron energy, then fragmentation is optimal for identification, but formation of higher mass ions is reduced
Solution Approach 1:
The patent applies dynamics by making the electron energy variable rather than constant. The EI source is configured to operate at multiple electron energies (e.g., 10 eV, 20 eV, 30 eV, 40 eV, 50 eV, 60 eV, 70 eV, 80 eV, 90 eV, 100 eV, 110 eV, 120 eV, 130 eV, 140 eV, 150 eV) that can be changed during a single experiment. This dynamic adjustment allows optimization of both molecular ion formation at lower energies and fragmentation at higher energies, resolving the contradiction between preserving higher mass ions and achieving optimal fragmentation for identification.
2Quantity of substance
If EI energy is reduced below 70 eV to favor molecular ion formation, then soft ionization is achieved, but switching to soft ionization techniques increases cost and complexity
Solution Approach 1:
The patent applies universality by designing an EI source that can perform both hard ionization (at 70 eV) and soft ionization (at lower energies like 10-50 eV) functions within a single device. The electron energy can be dynamically adjusted during a single experiment to favor molecular ion formation when needed, eliminating the need to switch between different ionization techniques or instruments. This multi-functional capability reduces both cost and complexity while maintaining the ability to produce abundant molecular ions.
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
Enables the production of abundant molecular and high mass ions, improving chemical identification and expanding the applicability of EI beyond standard 70 eV operations, making it a more universal ionization method by generating informative mass spectra across a range of analytes.
Implementation Method 1
A heated filament is employed to emit energetic electrons
Implementation Method 2
Ionization of the sample material occurs as a result of the electron beam bombarding the sample material
Data Source
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AI summary
Mass spectrometry is performed utilizing an electron ionization (EI) source. The EI source ionizes a sample at different electron energies, including below and above 70 eV. The EI source may be utilized for soft ionization as well as hard ionization. The value of the electron energy may be selected so as to favor the formation of molecular ions or other ions of high analytical value. The ion source may be an axial ion source.