Ion Transfer Tube With Alternating DC Fields
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Solution Overview
Problem
Existing ion transfer arrangements in mass spectrometers suffer significant ion loss due to collisions with the tube wall and space charge effects, particularly at atmospheric pressure to high vacuum transitions, limiting instrument sensitivity and efficiency.
Innovation Solution
An ion transfer arrangement utilizing a DC electrode assembly with alternating electrode widths and voltages to create spatially alternating electric fields, focusing ions away from the channel wall and toward the centerline, thereby reducing ion loss and improving transmission efficiency across a broader range of pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a simple ion transfer tube is used, then the device complexity is low, but ion loss due to wall collisions is significant
Solution Approach 1:
The ion transfer tube is segmented into multiple zones along its length, with each zone containing alternating high-voltage and low-voltage electrodes. This segmentation allows the creation of spatially alternating electric fields that focus ions toward the tube centerline in each zone, reducing wall collisions while maintaining manageable electrode complexity through modular design
Solution Approach 2:
Different regions of the ion transfer tube are assigned different voltage patterns and electrode configurations optimized for local conditions. The alternating high-voltage and low-voltage electrodes create localized electric field patterns that adapt to the varying pressure gradient and ion density along the tube length, improving overall ion transmission efficiency
2Temperature
If the ion transfer tube is heated to evaporate solvent, then desolvation is improved, but ion loss through wall collisions increases
Solution Approach 1:
The alternating electric field focusing mechanism is applied upstream in the ion transfer tube where ions are first introduced. This preliminary focusing action prevents ions from approaching the tube walls before they can be lost, while heating is applied downstream to achieve desolvation. The focused ion beam remains centralized and away from heated walls, eliminating the trade-off between desolvation and ion loss
3Ease of manufacture
If a dielectric tube is used, then manufacturing is simplified, but charge accumulation occurs inhibiting ion flow
Solution Approach 1:
The alternating high-voltage and low-voltage electrodes create regions of controlled potential distribution along the ion transfer tube. This equipotential structure prevents charge accumulation on dielectric surfaces by maintaining controlled electric field patterns that guide ions through the tube without allowing charge buildup, while still allowing the use of dielectric materials for tube construction
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 solution effectively reduces ion loss and enhances ion transmission efficiency by creating alternating electric fields that prevent ions from colliding with the channel wall, even at low pressures, thereby improving instrument sensitivity and throughput.
Implementation Method 1
DC electrode assembly with alternating electrode widths and voltages to create spatially alternating electric fields
Implementation Method 2
Ions, together with charged and uncharged particles... enter the inlet end of the ion transfer capillary and traverse its length under the influence of the pressure gradient
Data Source
AI summary
An ion transfer arrangement for transporting ions between higher and lower pressure regions of a mass spectrometer includes an electrode assembly (120) with a first plurality of ring electrodes (205) arranged in alternating relation with a second plurality of ring electrodes (210). The first plurality of ring electrodes (205) are narrower than the second plurality of ring electrodes (210) in a longitudinal direction, but the first plurality of ring electrodes have a relatively high magnitude voltage of a first polarity applied to them whereas the second plurality of ring electrodes (210) have a relatively lower magnitude voltage applied to them, of opposing polarity to that applied to the first set of ring electrodes (205). In this manner, ions passing through the ion transfer arrangement experience spatially alternating asymmetric electric fields that tend to focus ions away from the inner surface of the channel wall and towards the channel plane or axis of symmetry.