Portable Mass Spectrometer Atmospheric Pressure Interface Design
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Solution Overview
Problem
Portable mass spectrometers face challenges in achieving high sensitivity due to low pumping capacity, leading to inefficient transfer of atmospheric pressure ions into the vacuum, resulting in ion loss and reduced sensitivity compared to lab-based systems.
Innovation Solution
A portable mass spectrometer design utilizing a low gas flow inlet capillary optimized for minimal ion loss, combined with a turbomolecular pump system that maintains a pressure below 50 mTorr, and an RF ion guide for efficient ion collection and focusing, allowing direct ion introduction into the vacuum section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional API design with multiple differentially pumped vacuum sections is used, then ion guidance and focusing can be achieved, but the device size and pumping capacity requirements increase significantly
Solution Approach 1:
The patent extracts and eliminates the first vacuum section (typically at 1 Torr) from the conventional differential pumping scheme. By removing this intermediate section, the system reduces the number of vacuum stages from multiple sections to a simplified two-stage configuration, directly reducing device size and pumping capacity requirements while maintaining ion guidance through the remaining vacuum section
Solution Approach 2:
The patent segments the vacuum system into only two essential sections: the atmospheric pressure ion source region and a single vacuum analysis region. This segmentation eliminates redundant vacuum sections while preserving the essential function of ion guidance and focusing, achieving size reduction without sacrificing measurement precision
2Measurement precision
If the gas throughput is increased to improve MS sensitivity, then more ions can be introduced, but larger pumps are required to maintain vacuum
Solution Approach 1:
By removing the first vacuum section that typically handles high gas throughput, the patent eliminates the need for large-capacity pumps. The direct coupling of the ion source to the vacuum analysis region allows efficient ion transfer with minimal gas load on the pump, enabling high sensitivity with compact pumping systems
Solution Approach 2:
The patent changes the pressure parameter profile by eliminating the intermediate 1 Torr section, allowing the system to operate efficiently at lower overall gas throughput while maintaining high ion transmission. This parameter change enables the use of smaller pumps with lower pumping capacity requirements
3Measurement precision
If multiple inlet capillaries and ion funnel technology are used to increase gas throughput, then MS sensitivity improves, but the device complexity and size increase
Solution Approach 1:
The patent removes the need for multiple inlet capillaries and ion funnel components by implementing a simplified direct-coupling interface. This extraction of unnecessary components reduces interface complexity while maintaining or improving sensitivity through efficient direct ion transfer from the ion source to the vacuum region
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 achieves sensitivity comparable to commercial desktop mass spectrometers while reducing gas flow rate and pump size, minimizing ion loss and maintaining effective ion guiding and focusing at lower pressures.
Implementation Method 1
The one or more turbomolecular pumps pump out a majority of the gas directed into the at least one vacuum section by the at least one gas inlet
Implementation Method 2
The mass spectrometer has a radio frequency (RF) ion guide in the at least one vacuum section positioned for collecting the ions from the at least one gas inlet and transmitting the ions further to a mass analyzer
Data Source
AI summary
A portable mass spectrometer having an atmospheric pressure interface for introducing ions generated at ambient pressure gas conditions into a vacuum of the mass spectrometer. The mass spectrometer has a vacuum chamber having at least one vacuum section and at least one gas inlet for directing the ambient pressure gas including the ions into the at least one vacuum section. The at least one gas inlet has a gas passage channel of a length L and a limiting cross section S with a ratio of L/S being less than 20,000 cm−1. The mass spectrometer has a radio frequency (RF) ion guide in the at least one vacuum section positioned for collecting the ions from the at least one gas inlet and transmitting the ions further to a mass analyzer for analyzing the ions transmitted from the ion guide.