Ion Guide Axial Field Gradient for Mass Spectrometer Throughput

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Solution Overview

Problem

In mass spectrometers, ion guides in high-pressure regions cause ions to slow down due to collisions with background/collision gas, leading to prolonged residence times, reduced sample throughput, and decreased sensitivity, especially in triple quadrupole mass spectrometers operating in multiple reaction monitoring mode.

Innovation Solution

The introduction of a multipole ion guide with resistive or conductive inserts and a DC voltage supply to establish an axial electric field gradient along the device centerline, which helps move ions through the ion guide without distorting the radially-confining RF field, thereby reducing ion residence time and maintaining transmission efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a static axial field is established to increase ion transport rate, then ion transport speed is improved, but radial field distortion occurs causing ion beam defocusing

Engineering Contradiction:

Improveion transport speedVSAvoidion beam focusing

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

Resistive inserts are introduced as intermediary elements between the electrodes to generate the axial electric field. These inserts are positioned within the gaps of the electrode structure and have controlled electrical properties that allow them to produce the desired axial field while minimizing disruption to the radial confining field, thus mediating between the conflicting requirements of ion transport speed and beam focusing

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The axial electric field is generated locally at specific positions where resistive inserts are placed within the electrode gaps, rather than applying a uniform field throughout the entire ion guide. This localized approach allows the axial field to be established only where needed for ion transport acceleration, while preserving the integrity of the radial confining field in other regions

Inventive Principle:

Principle #3Local quality

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 transport efficiency, reducing ion residence time and maintaining sensitivity by minimizing RF field distortion, thus allowing for increased sample throughput and improved performance in mass spectrometers.

Implementation Method 1

The RF voltage supply may be configured to apply a RF voltage to the plurality of electrodes that establishes a RF field to radially confine ions

Methodology Applied

Scientific EffectRadio-frequency field:

Implementation Method 2

The DC voltage supply may be configured to apply a first DC voltage to a first location of the resistive insert and a second DC voltage to a second location of the resistive insert that establishes an axial electric field gradient along at least a portion of the device centerline

Methodology Applied

Scientific EffectAxial electric field gradient: Electric Field

Implementation Method 3

ions entering the ion guide undergo fragmentation via the collision-induced dissociation mechanism

Methodology Applied

Scientific EffectCollision-induced dissociation:

Data Source

PatentUS8785847B2Mass spectrometer having an ion guide with an axial field

Publication Date: 2014.07.22 THERMO FINNIGAN LLC

AI summary

A mass spectrometer having an ion guide with an axial field is described. The ion guide includes electrodes with longitudinally extending gaps and inserts configured to be proximate to the gaps.