Dual Ion Source Mass Spectrometer for Simultaneous Positive and Negative Ionization
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Solution Overview
Problem
Mass spectrometers often struggle to identify and quantify molecules effectively due to the loss of molecular ions during electron-impact ionization, which limits data granularity and selectivity, especially when analyzing complex mixtures.
Innovation Solution
A dual ion source system combining an electron-impact ion source and a trochoidal electron monochromator is used to generate both positive and negative ions, allowing for simultaneous production of mass fragment spectra and molecular ions with minimal sensitivity loss, enhancing data granularity and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electron-impact ionization is used to generate mass spectra, then molecular ion identification is achieved, but molecular ions are lost due to fragmentation
Solution Approach 1:
The ionization process is segmented into two distinct pathways: positive ion mode and negative ion mode. Each mode uses optimized electron energy levels to produce different ion types, allowing molecular ions to be preserved in one mode while achieving fragmentation information in another mode.
Solution Approach 2:
The electron energy parameter is changed between positive and negative ion sources. The positive ion source uses higher electron energy (70 eV) to produce fragmentation patterns, while the negative ion source uses lower electron energy to preserve molecular ions, thus resolving the contradiction between identification and preservation.
2Loss of information
If high-energy electrons are used for ionization, then mass fragment spectra are generated, but molecular ion preservation is reduced
Solution Approach 1:
The system segments the ionization function into two separate ion sources: one dedicated to generating fragment spectra through high-energy electron impact, and another dedicated to preserving molecular ions through low-energy electron capture. This segmentation allows both information types to be obtained simultaneously without compromise.
Solution Approach 2:
Instead of using a single high-energy electron source that causes fragmentation, the invention inverts the approach by using a low-energy electron source for molecular ion preservation while obtaining fragment information from the high-energy source, thus achieving both goals through opposite energy approaches.
3Device complexity
If a single ion source is used, then device complexity is reduced, but data granularity and selectivity are limited
Solution Approach 1:
The invention merges two ion sources with different ionization mechanisms (electron impact and electron capture) into a single integrated mass spectrometer system. This combining approach provides enhanced data granularity and selectivity while maintaining manageable system complexity through unified control and analysis.
Solution Approach 2:
The mass spectrometer is designed with multi-functionality to accommodate both positive and negative ion sources, allowing it to perform multiple types of analyses (fragmentation patterns, molecular ion identification, compound class identification) within a single instrument, thus improving data granularity without proportionally increasing complexity.
4Loss of substance
If electron capture ionization is used to generate negative ions, then molecular anions are produced, but positive ion fragment spectra are not obtained
Solution Approach 1:
The system segments the ionization information into two complementary channels: negative ion mode for molecular anion production and positive ion mode for fragment spectra generation. Both channels operate simultaneously, ensuring that neither type of information is lost while maintaining the strengths of each ionization method.
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 confident identification and quantification of target molecules by producing dual mass spectra with enhanced selectivity and sensitivity, preserving molecular ions and reducing fragmentation, thus improving the analysis of complex mixtures.
Implementation Method 1
The first ion source emits high-energy electrons ( ̃70 eV) to generate characteristic positively-charged mass fragment spectra
Implementation Method 2
the second source emits low-energy electrons in a narrow bandwidth to generate negative molecular ions or other ions via electron capture ionization
Data Source
AI summary
Among other things, we describe methods and apparatus for the ionization of target molecular analytes of interest, e.g., for use in mass spectrometry. In some implementations, a thin molecular stream is emitted in either single or a split mode and encounters both an electron-impact ion source and trochoidal electron monochromator placed sequentially or coincidentally. The first ion source emits high-energy electrons (˜70 eV) to generate characteristic positively-charged mass fragment spectra while the second source emits low-energy electrons in a narrow bandwidth to generate negative molecular ions or other ions via electron capture ionization. The dual ion source may be coupled to analytical instruments such as a gas chromatograph and to any number of mass analyzers such as a polarity switching quadrupole mass analyzer or to multiple mass analyzers.