Semi-open EI Source Coupled to MR-TOF Analyzer
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Solution Overview
Problem
Current GC-MS instruments face limitations in sensitivity, particularly due to mass spectral interferences with the matrix and chemical background, which hinder the achievement of a detection limit below 1-10 fg, despite advancements in ionization efficiency and analyzer resolution.
Innovation Solution
The implementation of a semi-open electron impact (so-EI) source coupled with a high-resolution multi-reflecting time-of-flight (MR-TOF) analyzer, along with specific ion optical coupling and pulsing schemes, enhances ion transmission and reduces time-of-flight aberrations, allowing for improved differentiation between sample and chemical background, thereby increasing sensitivity and dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If quadrupole analyzers are used in GC-MS, then device complexity is reduced and cost is lowered, but detection limit deteriorates to approximately 1 pg due to mass scanning losses and low resolution
Solution Approach 1:
The patent replaces the mechanical scanning system of quadrupole analyzers with a time-of-flight (TOF) analyzer that uses electromagnetic field manipulation. The TOF analyzer accelerates ions through electric fields and measures their flight time, eliminating the mechanical scanning limitations of quadrupoles and achieving both high resolution (R≥20,000) and improved detection limits (≤100 fg) without proportionally increasing device complexity
2Quantity of substance
If semi-open EI source is implemented, then ionization efficiency improves and sample concentration increases, but device complexity increases due to additional ion optical elements
Solution Approach 1:
The patent introduces an intermediate differential pumping stage between the semi-open EI source and the TOF analyzer. This intermediary chamber with controlled pressure gradient (10^-3 to 10^-6 Torr) serves as a buffer that allows efficient ion transmission from the source while protecting the high-vacuum TOF analyzer, thereby reducing the complexity burden of direct coupling
Solution Approach 2:
The patent segments the vacuum system into distinct pressure zones: the EI source operates at higher pressure (10^-3 Torr) for efficient ionization, the intermediate chamber provides pressure transition (10^-4 to 10^-6 Torr), and the TOF analyzer maintains ultra-high vacuum (≤10^-7 Torr). This segmentation allows each component to operate in its optimal pressure environment without requiring overly complex coupling mechanisms
3Measurement precision
If high resolution MR-TOF analyzer is used, then mass spectral interference is reduced and detection limit improves, but device complexity and instrumental requirements increase
Solution Approach 1:
The patent designs the MR-TOF analyzer to perform multiple functions: it achieves high resolution mass analysis (R≥20,000), provides enhanced detection limits (≤100 fg), and incorporates MS-MS capabilities through collision-induced dissociation (CID) in the same instrument. This multi-functionality reduces the need for separate specialized instruments, effectively managing device complexity while delivering superior performance
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 configuration enhances the sensitivity and reliability of GC-MS analysis by improving the detection limit and dynamic range, enabling better separation of analytes from chemical background and matrix interference, and reduces instrumental complexity.
Implementation Method 1
a semi-open nEI source... The semi-open EI source is arranged in a separate differential pumping stage, provides ion storage in an electron beam
Implementation Method 2
a multi-reflecting time-of-flight analyzer... The interface includes a set of focusing and deflecting ion-optical elements coupling the ion source with the analyzer
Implementation Method 3
The interface includes a set of focusing and deflecting ion-optical elements coupling the ion source with the analyzer such that the spatial emittance of the ion source is matched to the acceptance of the analyzer and that time broadening of the ion signal due to the spatial emittance is eliminated at the detector
Data Source
AI summary
For improving sensitivity, dynamic range, and specificity of GC-MS analysis there are disclosed embodiments of novel apparatuses based on improved characteristics of semi-open source with electron impact ionization, providing much higher brightness compared to known open EI sources. In an implementation, the source becomes compatible with multi-reflecting TOF analyzers for higher resolution analysis for improving detection limit. With improved schemes of spatial and temporal refocusing there are proposed various tandem TOF-TOF spectrometers with PSD, CID, and SID fragmentation and using either singly reflecting TOF or MR-TOF analyzers.