Discontinuous Atmospheric Pressure Interface for Mass Spectrometers
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Solution Overview
Problem
Current atmospheric pressure interfaces (APIs) for mass spectrometers suffer from low ion transfer efficiency, particularly in portable instruments, due to limited pumping capacity, leading to significant ion loss during the transfer process from atmospheric to vacuum conditions.
Innovation Solution
A discontinuous atmospheric pressure interface system that controls the movement of ions and air/gas using a valve and capillaries, allowing for maximum ion introduction during open periods and optimizing vacuum pressure for mass analysis by shutting the channel after ion introduction, thereby enhancing ion transfer efficiency with limited pumping capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a constantly open channel with differential pumping stages is used for ion transfer, then continuous ion flow is maintained, but ion transfer efficiency is low due to limited pumping capacity in portable instruments
Solution Approach 1:
The patent implements periodic opening and closing of the transfer channel using a valve mechanism. The channel is opened briefly to allow ion transfer, then closed to enable rapid pressure equalization between regions. This periodic action converts a continuous low-efficiency transfer into discrete high-efficiency transfer events, resolving the contradiction between continuous flow and transfer efficiency.
Solution Approach 2:
The system dynamically adjusts the pressure differential across the transfer channel by controlling valve timing. Rather than maintaining a constant pressure gradient with complex multi-stage pumping, the system creates dynamic pressure changes through coordinated valve operation, simplifying the pumping requirements while maximizing ion transfer during open periods.
2Reliability
If the transfer channel is kept open continuously, then ion flow is maintained, but vacuum pressure deteriorates due to limited pumping capacity
Solution Approach 1:
The valve is operated periodically to close the transfer channel during mass analysis, isolating the vacuum region from atmospheric pressure. This periodic isolation maintains stable vacuum pressure while allowing efficient ion transfer during brief open periods, resolving the contradiction between pressure stability and transfer efficiency.
Solution Approach 2:
The system performs preliminary ion transfer during the open period before closing the valve, ensuring all necessary ions are transferred before vacuum isolation. This preliminary action allows the vacuum region to be sealed off and maintained at stable pressure for analysis without compromising ion transfer efficiency.
3Reliability
If multiple differential pumping stages are used, then vacuum pressure is maintained, but device complexity and size increase
Solution Approach 1:
The patent extracts the complex multi-stage pumping system and replaces it with a simplified single-stage or reduced-stage pumping system combined with periodic valve control. The valve mechanism temporarily isolates pressure regions, eliminating the need for multiple continuous pumping stages, thereby reducing instrument weight while maintaining vacuum pressure stability.
Solution Approach 2:
The valve acts as an intermediary mechanism that temporarily connects or isolates pressure regions. Instead of using multiple pumping stages to continuously manage pressure gradients, the valve mediates pressure equalization and isolation, simplifying the pumping system requirements and reducing overall instrument weight.
4Reliability
If a small ID capillary or thin hole is used for ion entry, then vacuum pressure is maintained, but ion transfer efficiency decreases
Solution Approach 1:
The system uses periodic valve opening to allow ions to enter the vacuum region through a larger aperture than would be permissible in continuous operation. During brief open periods, the larger effective opening area enables high ion transfer efficiency, while the periodic closure maintains vacuum pressure control, resolving the contradiction between aperture size and pressure control.
Solution Approach 2:
The effective aperture area is dynamically controlled through valve timing rather than being fixed by a small ID capillary. The valve creates dynamic control over the effective opening size, allowing large effective area during transfer phases while maintaining small physical aperture during vacuum phases, thus achieving both high transfer efficiency and pressure control.
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
The discontinuous API system significantly increases ion transfer efficiency, achieving comparable performance to lab-scale instruments while maintaining optimal vacuum conditions for mass analysis, even in portable devices with reduced pumping capacity.
Implementation Method 1
transfer ions from a region at atmospheric pressure into other regions at reduced pressures
Implementation Method 2
a first capillary inserted into a first end of the tube and a second capillary inserted into a second end of the tube
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
A method of interfacing atmospheric pressure ion sources, including electrospray and desorption electrospray ionization sources, to mass spectrometers, for example miniature mass spectrometers, in which the ionized sample is discontinuously introduced into the mass spectrometer. Discontinuous introduction improves the match between the pumping capacity of the instrument and the volume of atmospheric pressure gas that contains the ionized sample. The reduced duty cycle of sample introduction is offset by operation of the mass spectrometer under higher performance conditions and by ion accumulation at atmospheric pressure.