Ion Trap Space Charge Control via Segmented Mass Analysis

Solution Overview

Problem

Ion traps in mass spectrometers face distortion in mass spectra due to excess space charge from overfilling, which interferes with accurate analysis, particularly in certain trap scan techniques.

Innovation Solution

A method involving filling the ion trap with fragmented ions of selected mass-to-charge ranges, cooling them, applying RF and resolving DC voltages to eliminate ions outside the desired range, and scanning the retained ions for detection, thereby reducing space charge effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the ion trap is filled with ions to increase signal intensity, then the sensitivity of detection is improved, but space charge effects cause mass spectrum distortion

Engineering Contradiction:

Improvemass spectrum accuracyVSAvoidion population in trap

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The overall mass-to-charge range is divided into multiple selected mass-to-charge ranges, and the ion population is segmented by mass-to-charge ratio. This allows different mass ranges to be trapped and analyzed separately, preventing space charge distortion while maintaining detection sensitivity for each segment.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Ions are cooled to low temperatures before mass analysis to reduce their kinetic energy and minimize space charge effects. This preliminary cooling action prepares the ion population for accurate mass spectrometry by reducing the harmful effects of ion-ion interactions.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If ions are retained in the trap for mass analysis, then measurement precision is improved, but space charge interference increases

Engineering Contradiction:

Improveanalytical precisionVSAvoidspace charge interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

Ions are cooled to low temperatures before mass analysis to reduce their kinetic energy and minimize space charge effects. This preliminary cooling action prepares the ion population for accurate mass spectrometry by reducing the harmful effects of ion-ion interactions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The ion trap operates in periodic cycles: filling with ions of a specific mass range, cooling, analyzing, and ejecting. This periodic operation allows the trap to maintain low ion populations during analysis, reducing space charge interference while achieving high measurement precision through repeated measurements.

Inventive Principle:

Principle #19Periodic action

3Productivity

If the ion trap capacity is increased to analyze more ions, then productivity is improved, but mass spectrum distortion worsens

Engineering Contradiction:

Improveion analysis throughputVSAvoidmass spectrum accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The overall mass-to-charge range is divided into multiple selected mass-to-charge ranges, and the ion population is segmented by mass-to-charge ratio. This allows different mass ranges to be trapped and analyzed separately, preventing space charge distortion while maintaining detection sensitivity for each segment.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The ion trap operates in periodic cycles: filling with ions of a specific mass range, cooling, analyzing, and ejecting. This periodic operation allows the trap to maintain low ion populations during analysis, reducing space charge interference while achieving high measurement precision through repeated measurements.

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

This approach effectively reduces space charge interference, leading to improved mass spectrum accuracy by selectively retaining and ejecting ions within specific mass-to-charge ranges, enhancing the analytical precision of mass spectrometry.

Implementation Method 1

applying an RF voltage and a resolving direct current voltage to the ion trap for eliminating any remaining fragmented ions outside the selected ion mass-to-charge range

Methodology Applied

Scientific EffectIon mobility separation: Electrophoresis

Implementation Method 2

cooling the fragmented ions trapped in the ion trap for a first cooling period; cooling the retained ions in the ion trap for a second cooling period

Methodology Applied

Scientific EffectGas kinetic cooling: Cooling

Data Source

PatentUS9318310B2Method to control space charge in a mass spectrometer

Publication Date: 2016.04.19 DH TECH DEVMENT PTE

AI summary

A method for operating a mass spectrometer having an ion trap over a plurality of selected mass-to-charge ranges constituting an overall mass-to-charge range is disclosed. For each of the plurality of selected mass-to-charge ranges the method comprises filling the ion trap with fragmented ions of the selected mass-to-charge ranges, cooling the fragmented ions trapped in the ion trap for a first cooling period, applying an RF voltage and a resolving direct current voltage to the ion trap for eliminating any remaining fragmented ions outside the selected ion mass-to-charge range and retaining ions within the selected ion mass-to-charge range, cooling the retained ions in the ion trap for a second cooling period, and scanning the retained ions out of the ion trap and detecting the ions released therefrom.