Ion Transfer Arrangement 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 when transporting ions from atmospheric pressure to high vacuum conditions, limiting instrument sensitivity and efficiency.

Innovation Solution

An ion transfer arrangement with a conduit having a plurality of apertures in its sidewall to allow gas flow reduction, combined with alternating DC fields and differential pumping, which focuses ions away from the wall and reduces pressure inside the conduit, enhancing desolvation and ion transmission efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If ions are transported through a long ion transfer tube from atmospheric pressure to high vacuum, then ion transmission distance is achieved, but ion loss due to wall collisions increases significantly

Engineering Contradiction:
Improveion transfer tube lengthVSAvoidion loss
Core Design Contradiction:
Length of moving objectVSLoss of substance

Solution Approach 1:

The ion transfer tube is divided into multiple sections with alternating polarity electrodes, creating segmented electric field regions that collectively guide ions through the long tube while minimizing wall collisions at any given position

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent employs dynamic alternating polarity electric fields that change over time to actively steer ions through the tube, adapting the field configuration to maintain ion focus and prevent wall collisions throughout the extended tube length

Inventive Principle:
Principle #15Dynamics

2Loss of substance

If a simple aperture is used instead of a long ion transfer tube, then ion loss is reduced, but desolvation of ion clusters is insufficient

Engineering Contradiction:
Improveion lossVSAvoiddesolvation efficiency
Core Design Contradiction:
Loss of substanceVSTemperature

Solution Approach 1:

The patent applies preliminary heating and electric field acceleration to ions before they enter the main transfer region, pre-desolvating ion clusters and preparing them for efficient transmission through the aperture with minimal wall collisions

Inventive Principle:
Principle #10Preliminary action

3Quantity of substance

If space charge effects are present in the ion beam, then ion density is maintained, but ion loss due to repulsion increases

Engineering Contradiction:
Improveion densityVSAvoidion loss
Core Design Contradiction:
Quantity of substanceVSLoss of substance

Solution Approach 1:

The alternating polarity electric fields are applied periodically to counteract space charge repulsion effects, using rhythmic field reversals to maintain ion beam coherence and reduce losses from electrostatic repulsion among densely packed ions

Inventive Principle:
Principle #19Periodic action

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 significantly reduces ion loss and increases the number of ions reaching the mass analyzer by promoting laminar flow, desolvation, and maintaining ions focused through the skimmer, thereby enhancing instrument sensitivity and throughput.

Implementation Method 1

application of an axial DC field... the parabolic velocity profile of the gas stream (relative to the ions) produces a gas dynamic force that focuses ions to the tube centerline

Methodology Applied
Scientific EffectElectrophoresis: Electrophoresis

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

Methodology Applied
Scientific EffectPressure gradient: Pressure Gradient

Implementation Method 3

the ion transfer tube may be heated to evaporate residual solvent (thereby improving ion production)

Methodology Applied
Scientific EffectEvaporation: Evaporation

Data Source

PatentUS8148680B2Ion transfer arrangement with spatially alternating DC and viscous ion flow
Publication Date: 2012.04.03 THERMO FISHER SCI BREMEN
  • US8148680B2 patent drawing
  • US8148680B2 patent drawing
  • US8148680B2 patent drawing

AI summary

A method of transporting gas and entrained ions between higher and lower pressure regions of a mass spectrometer comprises providing an ion transfer conduit 60 between the higher and lower pressure regions. The ion transfer conduit 60 includes an electrode assembly 300 which defines an ion transfer channel. The electrode assembly 300 has a first set of ring electrodes 305 of a first width D1, and a second set of ring electrodes of a second width D2 (≧D1) and interleaved with the first ring electrodes 305. A DC voltage of magnitude V1 and a first polarity is supplied to the first ring electrodes 205 and a DC voltage of magnitude V2 which may be less than or equal to the magnitude of V1 but with an opposed polarity is applied to the second ring electrodes 310. The pressure of the ion transfer conduit 60 is controlled so as to maintain viscous flow of gas and ions within the ion transfer channel.