Quadrupole Mass Filter Pre-Electrode Asymmetry

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Solution Overview

Problem

Quadrupole mass spectrometers face low ion passing efficiency due to ions dispersing in the unstable region when entering the quadrupole mass filter, leading to reduced detection sensitivity, especially for analyzing minor components in samples.

Innovation Solution

The quadrupole mass filter design includes a pre-electrode section with non-rotationally symmetric pre-rod electrodes and tailored voltage applications to improve the matching characteristic between ion emittance and acceptance, reducing ion loss and enhancing overall ion passing efficiency by making the acceptance shape in the pre-electrode section elliptical, matching the elliptical acceptance in the main electrode section.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If ions are introduced into the quadrupole mass filter through the end part, then ions can enter the filter space, but ions disperse in the unstable region causing low passing efficiency

Engineering Contradiction:

Improveion passing efficiencyVSAvoidion stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

A pre-electrode section is provided before the main rod electrodes to preliminarily guide and condition the ions before they enter the main quadrupole field. This preliminary action prepares the ions for stable transmission by adjusting their trajectories in advance, reducing dispersion in the unstable region and improving overall passing efficiency.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The pre-electrode section acts as an intermediary between the ion source and the main quadrupole mass filter. It mediates the transition of ions from the unstable region to the stable region by providing a gradual adaptation zone that reduces ion dispersion and improves transmission efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If conventional symmetric pre-rod electrodes are used, then the structure is simple, but the acceptance shape does not match the elliptical acceptance in the main electrode section

Engineering Contradiction:

Improveion introduction efficiencyVSAvoidelectrode configuration

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The pre-rod electrodes are configured with different radii from the main rod electrodes, creating an asymmetric structure. This asymmetry transforms the circular acceptance shape in the pre-electrode section to an elliptical shape that matches the acceptance characteristics of the main electrode section, thereby improving ion introduction efficiency without excessive complexity.

Inventive Principle:

Principle #4Asymmetry

3Quantity of substance

If the radius of pre-rod electrodes is made equal to main rod electrodes, then the structure is uniform, but ion loss occurs due to mismatched acceptance shapes

Engineering Contradiction:

Improveion transmission amountVSAvoidacceptance shape matching

Core Design Contradiction:

Quantity of substanceVSShape

Solution Approach 1:

The pre-rod electrodes are given different local qualities (different radii) compared to the main rod electrodes. This local differentiation optimizes the acceptance shape in the pre-electrode section to be elliptical, matching the main electrode section's acceptance characteristics, thereby reducing ion loss and improving overall ion transmission amount.

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 significantly increases the ion passing efficiency, allowing more ions to reach the detector and improving detection sensitivity, making it suitable for identifying and measuring minor components in samples.

Implementation Method 1

A voltage obtained by adding a direct current voltage and a radio-frequency voltage (alternating current voltage) is applied to each of the four rod electrodes

Methodology Applied

Scientific EffectSuperposition of voltages:

Implementation Method 2

behavior of ions in a quadrupole electric field generated in the space surrounded by the rod electrodes by the voltage applied to the rod electrodes

Methodology Applied

Scientific EffectQuadrupole electric field: Electric Field

Implementation Method 3

movement of ions passing through an ideal quadrupole electric field generated in the space surrounded by the rod electrodes extending in the z axis is represented by the following Equations (1) which are called the Mathieu equations

Methodology Applied

Scientific EffectMathieu equations:

Data Source

PatentUS10707066B2Quadrupole mass filter and quadrupole mass spectrometrometer

Publication Date: 2020.07.07 SHIMADZU CORP

AI summary

Four main rod electrodes included in a main electrode section are disposed in a rotationally symmetric manner around an ion optical axis. Among four pre-rod electrodes included in a pre-electrode section disposed in front of the main electrode section, two are in contact with a circle of a radius r0, whereas the other two are disposed to be in contact with a circle of a radius R0 larger than r0, resulting in rotational asymmetry around the ion optical axis. Accordingly, a shape of acceptance on an x-y plane regarding positions of ions in the pre-electrode section becomes elliptical. This allows the shape of the acceptance to become gradually flat as the ions travel along the ion optical axis, reducing a mismatch between emittance of incoming ions and the acceptance on a receiving side, and relieving ion loss during ion introduction.