Ion Bunching for Mass Spectrometry Transport
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Solution Overview
Problem
In mass spectrometry, transporting ions through regions with background gas pressure in the range of 1 mTorr to several tens of Torr requires large potential gradients, which can lead to electrical breakdown and is challenging to implement effectively, especially when ions need to be transported over long paths.
Innovation Solution
The solution involves breaking the continuity of ion flow by bunching ions into spatially-separated packets, allowing temporary creation of regions with reduced potential gradients, enabling forward migration of individual ion packets while minimizing the overall gradient across the ion transport apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large potential gradients are applied to transport ions through regions with background gas pressure, then ion transport efficiency is improved, but electrical breakdown occurs and system reliability deteriorates
Solution Approach 1:
The ion transport path is divided into multiple discrete regions with individual electrodes. Each electrode can be independently controlled to create localized potential gradients, allowing efficient ion transport through each segment without requiring excessively high voltages across the entire path. This segmentation prevents electrical breakdown while maintaining transport efficiency.
Solution Approach 2:
The system employs periodic switching of DC potentials on electrodes to create time-varying potential gradients. By alternately establishing and collapsing potential wells, ions are periodically accelerated through the transport medium. This periodic action enables efficient ion transport while keeping instantaneous voltage requirements manageable, avoiding electrical breakdown.
2Speed
If large overall potential difference is applied to decrease ion drift time, then ion transport speed is improved, but voltage requirements become impractically high
Solution Approach 1:
The total potential difference required for fast ion transport is divided into multiple smaller potential steps across successive electrode segments. Each electrode contributes a modest voltage increment, collectively achieving the necessary total potential difference for rapid ion transit without requiring any single electrode to operate at impractically high voltages.
Solution Approach 2:
By periodically switching DC potentials on electrodes in sequence along the transport path, the system creates a moving potential gradient that continuously propels ions forward. This periodic potential switching achieves fast ion drift by maintaining a consistent forward-driving force without requiring the entire path to be at high potential simultaneously, thus reducing overall voltage requirements.
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 approach reduces the overall potential gradient across the ion transport apparatus, preventing electrical breakdown and allowing efficient ion transport without the need for large voltages, thus simplifying the system design and operation.
Implementation Method 1
The transient DC potentials or voltage waveforms applied to each segment generate a travelling wave 7 which moves in the axial direction and thereby urges or propels ions up or against the potential gradient of the reverse axial electric field.
Implementation Method 2
The raised potential of the upstream devices cause ions emerging from the second upstream device 4 to be accelerated through the potential difference, denoted as 'CE' in FIG. 1A, between the outlet of the second upstream device 4 and the entrance of the collision cell 5.
Implementation Method 3
application of electrical potentials that generate a reverse axial DC electric field together with generation of a 'traveling wave' that drives ions against the corresponding potential gradient.
Data Source
AI summary
A mass spectrometry method comprises: receiving a stream of ions at an inlet end of an ion transport device; accumulating a first portion of the ion stream at a first electrical potential well at a first position within the ion transport device between the inlet and outlet ends; creating a generally descending potential profile within the ion transport apparatus between a second position and the outlet end and, simultaneously, creating a second potential well at a third position within the ion transport apparatus, the second position disposed between the first position and the inlet end, the third position disposed between the second position and the inlet end; and transporting the accumulated first portion of the ion stream from the first position to the outlet end under the impetus of the generally descending potential profile and, simultaneously, accumulating a second portion of the ion stream at the second potential well.