Mass Spectrometer Dual Ion Source Branching
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Solution Overview
Problem
Existing mass spectrometers face challenges in efficiently switching between ion sources at different pressure levels, such as APCI and EI, which limits the ability to maintain high vacuum in EI ionization chambers and restricts ion introduction efficiency, especially when analyzing samples with mixed ingredients.
Innovation Solution
A mass spectrometer design that branches the sample gas from a GC column to both an APCI ion source and an EI ion source, with controlled flow rates and adjustable branching column lengths to allow for sequential ionization, enabling simultaneous or delayed introduction of sample components to each source, thereby balancing sensitivity and pressure maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single ion source is used for GC/MS analysis, then the device complexity is reduced, but the adaptability to different ionization methods (APCI and EI) is limited
Solution Approach 1:
The ion source system is segmented into multiple independent ion sources (APCI ion source and EI ion source) that operate in parallel. Each ion source is equipped with its own ionization chamber and can be independently controlled, allowing the system to switch between different ionization methods without increasing overall system complexity
Solution Approach 2:
The mass spectrometer is designed with multi-functionality to accommodate both APCI and EI ionization methods. The system includes a universal mass analysis chamber that can receive ions from either ion source, and a unified control system that manages both ionization methods, making the device adaptable to different analytical requirements
2Reliability
If sample gas is introduced to EI ion source at atmospheric pressure, then ionization efficiency is improved, but the vacuum in EI ionization chamber cannot be maintained
Solution Approach 1:
The system segments the pressure environments by providing separate ionization chambers for APCI (atmospheric pressure) and EI (vacuum). The EI ion source chamber is isolated from atmospheric pressure through its own vacuum system, allowing efficient ionization at vacuum conditions while the APCI ion source handles atmospheric pressure sampling
Solution Approach 2:
A differential pumping system acts as an intermediary between the atmospheric pressure APCI ion source and the vacuum EI ion source. This intermediary mechanism allows sample gas to be introduced at atmospheric pressure to the APCI source while maintaining vacuum conditions in the EI chamber through controlled pumping
3Stress or pressure
If a small introduction port is used between ionization chambers, then vacuum in EI chamber is maintained, but ion passage becomes difficult
Solution Approach 1:
The system eliminates the need for a small restrictive port by segmenting the ion paths. Each ion source (APCI and EI) has its own dedicated ion introduction path to the mass analysis chamber, allowing both chambers to operate at their optimal pressure levels without compromising ion transmission efficiency
Solution Approach 2:
The system transitions from a linear sequential arrangement (where a single port must serve both chambers) to a multi-dimensional configuration where multiple independent paths exist. This allows the EI chamber to maintain vacuum through its own port while the APCI chamber handles atmospheric pressure sampling separately, removing the bottleneck effect
4Reliability
If high flow rate gas is used for APCI corona discharge, then stable ionization is achieved, but sensitivity for trace analysis is reduced
Solution Approach 1:
The system dynamically allocates sample gas flow between the APCI and EI ion sources based on analytical requirements. The flow distribution can be adjusted in real-time, allowing high flow rates to the APCI source when stable ionization is needed, and low flow rates when trace analysis sensitivity is prioritized, providing flexible optimization for different analytical scenarios
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 allows for rapid identification of unknown ingredients by obtaining mass information from APCI and molecular structure information from EI ionization in a single measurement, enhancing the overall analytical capability and sensitivity.
Implementation Method 1
APCI/MS is an apparatus for ionizing and detecting micro-amount of ingredients in a mixed sample at high sensitivity by using ion-molecular reaction
Implementation Method 2
The EI source conducts ionization under a vacuum of about 10−3 Torr or less
Implementation Method 3
corona discharge using a needle electrode
Data Source
AI summary
A mass spectrometer capable of measuring under switching two ion sources at different pressure levels in which a sample gas separated by GC column is branched, and separately introduced to a first ion source (for example, APCI ion source) and a second ion source (for example, EI ion source) at a pressure level lower than that of the first ion source respectively. Preferably, the flow rate of the sample gas introduced to the APCI ion source is made more than the flow rate of the sample gas introduced to the EI ion source, so that the pressure for each of the ion sources can be maintained and analysis can be conducted by each ionization at a good balance in view of the sensitivity.