Ion Source Segmentation for Rapid EI to CI Switching
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Solution Overview
Problem
Existing mass spectrometers face challenges in quickly switching between electron ionization (EI) and chemical ionization (CI) modes, leading to contamination buildup and sensitivity issues due to continuous operation and overlapping kinetic energy distributions, which complicates ion selection and requires frequent disassembly for cleaning.
Innovation Solution
An ion source with separate, electrically isolated ion volumes and a controlled electron source structure that selectively supplies electrons to each volume, allowing for pulsed operation and rapid switching between EI and CI modes, minimizing contamination and optimizing ion separation through independent control of electron gates and potentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single ion source continuously performs both EI and CI ionization, then both ionization techniques can be utilized, but contaminants build up rapidly on ion volume surfaces reducing sensitivity
Solution Approach 1:
The ion source is divided into separate ionization regions (EI region and CI region) with distinct electron sources and ion volumes. This segmentation allows independent control of each ionization mode, enabling the system to perform both EI and CI without continuous contamination buildup in a single shared volume, thereby maintaining sensitivity while preserving versatility.
2Measurement precision
If electromagnetic fields are increased to improve ion separation between EI and CI volumes, then ion selection improves, but sensitivity is compromised
Solution Approach 1:
By segmenting the ion source into separate EI and CI regions with independent electron sources and ion volumes, the patent enables spatial separation of ionization processes. This physical segmentation allows for optimized electromagnetic field configurations in each region without compromising the other, achieving both good ion separation and maintained sensitivity.
3Adaptability or versatility
If ion sources are physically exchanged between EI and CI, then ionization mode can be switched, but the process takes one or more hours due to vacuum chamber venting and reestablishment
Solution Approach 1:
The patent merges both EI and CI ionization capabilities into a single integrated ion source assembly with separate but co-located ionization regions. This merging eliminates the need to physically exchange ion sources or vent the vacuum chamber when switching between ionization modes, reducing switching time from hours to moments while maintaining the ability to perform both EI and CI.
Solution Approach 2:
The ion source incorporates dynamic control mechanisms including independently controllable electron sources and ion volume potentials that can be rapidly switched between EI and CI modes. This dynamic control allows quick transitions between ionization types without mechanical intervention or vacuum disruption, achieving fast mode switching.
4Loss of time
If pressure interlocks are used to exchange ion sources without breaking vacuum, then switching time is reduced to several minutes, but this is still insufficient for single chromatographic run utilization
Solution Approach 1:
By merging EI and CI capabilities into a single ion source with rapidly switchable modes, the system eliminates the need for even minute-long source exchanges. This enables both ionization techniques to be utilized within a single chromatographic run, with mode switching occurring quickly enough to capture multiple analytes in one continuous operation, thereby maximizing productivity.
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 rapid and efficient switching between EI and CI modes, reducing contamination buildup, maintaining sensitivity, and allowing for simultaneous or sequential data collection within chromatographic runs without compromising ion separation.
Implementation Method 1
an electron beam is also supplied to the ion volume. The electrons directly strike the sample analytes, and the resulting energy exchange is sufficient to cause ionization, producing ions characteristic of the sample material
Implementation Method 2
The ion volume is configured so that the inflow of the reagent gas maintains a relatively high pressure within the ion volume, thereby ensuring a density for the reagent gas that increases the probability of collisions between the incoming electrons and the molecules of the reagent gas
Implementation Method 3
The CI and EI ion volumes are maintained at different potentials, thereby making it possible to electromagnetically select ions from either ion volume for analysis, while excluding ions from the other ion volume
Data Source
AI summary
An ion source includes structure having separate first and second ion volumes therein, and electron source structure having first and second portions that selectively supply electrons to the first and second ion volumes, respectively. The electron source structure has a first operational mode in which the second portion substantially prevents a supply of electrons to the second ion volume and in which electrons are supplied to the first ion volume under control of the first portion, and has a second operational mode in which the first portion substantially prevents a supply of electrons to the first ion volume and in which electrons are supplied to the second ion volume under control of the second portion.