Asymmetric Ion Trap Waveform for Mobility Separation

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Solution Overview

Problem

Conventional differential ion mobility analyzers operate at atmospheric pressure, leading to significant ion diffusion losses and low sensitivity due to the need for high voltage RF generators to achieve high-field mobility conditions, resulting in a low duty cycle for transmitting ions with differing mobility characteristics.

Innovation Solution

A differential ion mobility separator is designed with a plurality of electrodes that apply asymmetric voltage waveforms, DC voltages to create real potential fields, and symmetric RF voltages to form pseudo-potential fields, maintaining the system at pressures below 100 mbar to confine ions effectively and avoid diffusion losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If atmospheric pressure is used in differential ion mobility analyzers, then high voltage RF generators can provide high E/N values for high-field mobility conditions, but ion diffusion becomes a significant loss mechanism reducing sensitivity

Engineering Contradiction:

Improvehigh E/N values for high-field mobility conditionsVSAvoidion diffusion losses

Core Design Contradiction:

Use of energy by moving objectVSLoss of substance

Solution Approach 1:

The patent changes the pressure parameter from atmospheric to reduced pressure (below 100 mbar) to reduce ion diffusion losses while maintaining high E/N values through the asymmetric voltage waveform applied to the electrodes

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If atmospheric pressure is used, then high voltage RF generators are necessary to achieve high E/N values, but this results in low duty cycle for transmitting ions with differing mobility characteristics

Engineering Contradiction:

Improvehigh E/N valuesVSAvoidduty cycle for ion transmission

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The patent changes the pressure parameter to reduced pressure below 100 mbar, which allows high E/N values to be achieved without requiring high voltage RF generators, thereby improving the duty cycle for ion transmission

Inventive Principle:

Principle #35Parameter changes

3Loss of substance

If reduced pressure is used, then ion diffusion losses are reduced, but high voltage RF generators are no longer necessary and the mechanism for achieving high E/N values changes

Engineering Contradiction:

Improveion diffusion lossesVSAvoidhigh E/N values

Core Design Contradiction:

Loss of substanceVSUse of energy by moving object

Solution Approach 1:

The patent applies an asymmetric voltage waveform to the electrodes at reduced pressure, creating high E/N values during the high field portion of the waveform while maintaining low pressure to minimize ion diffusion losses

Inventive Principle:

Principle #4Asymmetry

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 enhances ion retention and separation efficiency, eliminating the need for high voltage RF generators and reducing ion loss during scanning, thereby improving sensitivity and duty cycle for differential ion mobility analysis.

Implementation Method 1

The mobility K of an ion in a gas in the presence of an electric field E is essentially independent of the field under conditions where the energy gained from the field by the ion is negligible compared with thermal energies

Methodology Applied

Scientific EffectIon mobility: Electrophoresis

Implementation Method 2

a device arranged and adapted to apply a DC voltage to at least some of the plurality of electrodes in order create a DC electric field within the differential ion mobility separator in the first radial direction which acts to retain at least some ions within the differential ion mobility separator

Methodology Applied

Scientific EffectElectric field: Electric Field

Implementation Method 3

a device arranged and adapted to apply a symmetric RF voltage to one or more of the electrodes so as to cause ions to be confined within the differential ion mobility separator in a second radial direction by a RF pseudo-potential field

Methodology Applied

Scientific EffectRF pseudo-potential field: Electromagnetic Induction

Data Source

PatentEP2637018B1Asymmetric field ion mobility in a linear geometry ion trap

Publication Date: 2018.04.18 MICROMASS UK LTD

Figure 1
Figure 2a~2b
Figure 3

AI summary

A linear ion trap is disclosed wherein an asymmetric voltage waveform is applied to electrodes forming the ion trap which causes ions to become radially separated in a first radial direction according to their differential ion mobility. In a mode of operation ions are ejected from the linear ion trap in the first radial direction and ions are confined within the trap in a second radial direction by a RF pseudo-potential field.