Quadrupole Mass Filter Charge-Up Elimination via Potential Gradient

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Solution Overview

Problem

Conventional methods for reducing charge-up in mass spectrometers, such as reversing the polarity of direct-current bias voltage, may not always effectively eliminate charge-up, leading to decreased detection sensitivity.

Innovation Solution

A mass spectrometer design that includes a direct-current voltage generator applying direct-current voltages of different polarities to adjacent electrodes during measurement preparation periods, creating a potential gradient to remove accumulated electric charges between electrodes, thereby preventing charge-up.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the polarity of direct-current bias voltage is temporarily reversed to eliminate charge-up, then charge-up is reduced, but detection sensitivity may still decrease when this method is insufficient

Engineering Contradiction:

Improvecharge-up elimination effectivenessVSAvoiddetection sensitivity

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The invention divides the voltage application strategy into two distinct segments: during measurement periods, normal direct-current bias voltage is applied to maintain ion transport; during waiting periods, reversed polarity voltage is applied to eliminate charge-up. This segmentation allows each function to be optimized independently without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention applies reversed polarity voltage during waiting periods before the next measurement begins, performing the charge-up elimination action in advance. This preliminary action ensures that when measurement starts, the ion transport optical element is free from charge-up effects, maximizing detection sensitivity from the outset.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If ions are transported through the ion transport optical element, then mass spectrometry measurement is enabled, but charge-up occurs on insulating surfaces reducing measurement accuracy

Engineering Contradiction:

Improvemeasurement capabilityVSAvoiddetection accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The invention implements periodic switching of voltage polarity: during measurement periods, normal voltage enables ion transport and mass spectrometry; during waiting periods, reversed polarity eliminates charge-up. This periodic action creates a cycle that continuously maintains measurement capability while periodically removing the harmful charge-up effect.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The invention converts the harmful charge-up effect into a beneficial cleaning mechanism. By applying reversed polarity voltage during waiting periods, the accumulated positive charges on insulating surfaces are neutralized or removed, effectively using the charge-up phenomenon itself as a means to clean the insulating surfaces of subsequent charge accumulation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach reliably eliminates charge-up, maintaining high detection sensitivity and accuracy by ensuring effective ion transport and convergence, even when conventional methods fail.

Implementation Method 1

transports ions while converging the ions by an effect of a radio-frequency electric field formed by the plurality of electrodes

Methodology Applied

Scientific EffectRadio-frequency electric field: Electric Field

Implementation Method 2

apply direct-current voltages of different polarities to electrodes adjacent to each other around the ion optical axis... creating a potential gradient to remove accumulated electric charges

Methodology Applied

Scientific EffectPotential gradient: Electric Field

Data Source

PatentUS11239069B2Mass spectrometer

Publication Date: 2022.02.01 SHIMADZU CORP

AI summary

When a Q-TOF type mass spectrometer is operated in an MS1 mode, a controller (40), at the time of measurement, controls voltage generators (31 to 33) such that only a V voltage (radio-frequency voltage for mass separation) and a direct-current bias voltage are applied to main rod electrodes of a quadrupole mass filter (12) without application of a U voltage (direct-current voltage for mass separation). During a measurement preparation period between a plurality of measurements to obtain one mass spectrum, the controller (40) controls a U voltage generator (31) so as to apply the U voltage to the main rod electrodes of the quadrupole mass filter (12). Accordingly, a direct-current electric field is formed between adjacent main rod electrodes around an ion optical axis (C) due to a potential difference, and electric charges accumulated in rod holders (122) holding the main rod electrodes are rapidly removed by an effect of this electric field. As a result, it is possible to eliminate a charge-up that has not been eliminated by a conventional method in which a polarity of a direct-current bias voltage applied to the rod electrodes is merely reversed.