Quadrupole Mass Filter Contamination Management
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Solution Overview
Problem
Quadrupole mass filters in mass spectrometers suffer from performance degradation due to contamination and energy differences between ions of varying mass-to-charge ratios, leading to transmission loss and calibration issues, requiring frequent cleaning and reducing analytical accuracy.
Innovation Solution
Implementing a method where the quadrupole mass filter alternates the application of attractive and repulsive DC voltages to each pair of electrodes, ensuring each pair spends equal time with each voltage, distributing contamination evenly and maintaining ion transmission efficiency by adjusting ion energy and recalibrating as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the quadrupole mass filter uses fixed attractive and repulsive DC voltages on the same opposing rod pairs, then the mass filtering function is achieved, but contamination builds up unevenly on the electrodes leading to performance degradation
Solution Approach 1:
The patent applies dynamics by making the electrode configuration movable rather than fixed. The controller dynamically switches between at least two different configurations of attractive and repulsive DC voltages on opposing rod pairs, allowing the system to adapt over time and prevent localized contamination buildup, thereby extending the operational duration before cleaning is required
Solution Approach 2:
The patent implements periodic action by alternately switching the DC voltage configurations on the quadrupole electrodes at predetermined intervals. This periodic switching ensures that contamination is distributed evenly across all electrodes over time, maintaining mass filtering performance and extending the time between cleanings
2Duration of action of stationary object
If ion energy is increased to spread contamination over larger surface area, then the time between cleanings is extended, but ion noding and poor isolation profiles occur reducing quantitative accuracy
Solution Approach 1:
Instead of statically increasing ion energy, the patent dynamically switches electrode configurations to achieve the goal of spreading contamination. This dynamic approach distributes contamination through voltage switching rather than energy increase, avoiding the harmful effects of ion noding while still extending the time between cleanings and maintaining quantitative accuracy
3Productivity
If the quadrupole mass filter operates with high ion load, then productivity is improved, but contamination buildup accelerates requiring more frequent cleaning
Solution Approach 1:
The patent applies periodic switching of electrode configurations that operates independently of ion load levels. This periodic action ensures that even under high ion load conditions, contamination is systematically distributed across all electrodes over time, allowing the system to maintain high productivity while extending the time between cleanings compared to fixed configurations
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 significantly extends the time between necessary cleanings, maintains high analytical accuracy, and reduces the impact of contamination on ion transmission, ensuring consistent performance over long-term operation.
Implementation Method 1
a voltage is applied between one pair of rods and the other, which comprises a radio frequency (RF) voltage with a DC offset voltage
Implementation Method 2
For given values of RF and DC voltages, ions of a certain mass-to-charge ratio (m/z) will be transmitted through the quadrupole while other ions will have unstable trajectories and collide with the electrodes
Implementation Method 3
An attractive DC voltage (e.g. negative) is applied to one pair of opposing rods and an equal magnitude repulsive DC voltage (e.g. positive) is applied to the other pair of opposing rods. The attractive and repulsive DC voltages impose a mass cut-off to the range of ion m/z ratios that can pass through the quadrupole filter
Data Source
AI summary
A method of operating a mass spectrometer, comprising: generating ions from a sample; mass filtering the ions using a quadrupole mass filter having a set of selection parameters to transmit ions within at least one selected range of mass-to-charge ratios narrower than an initial range, wherein the quadrupole comprises four parallel elongate electrodes arranged in opposing pairs to which are applied RF and DC, wherein an attractive DC voltage is applied to one pair of opposing electrodes and a repulsive DC voltage is applied to the other pair; mass analysing or detecting the ions transmitted by the quadrupole mass filter; repeating the steps of generating ions, mass filtering and mass analysing or detecting multiple times; switching a configuration of the pairs of opposing electrodes to which the attractive DC voltage and the repulsive DC voltage are applied multiple times over the course of repeating the steps so that over long term operation the build-up of contamination on each pair of opposing electrodes is substantially equal; and determining mass filtering steps for which quantitative accuracy should be maintained between them and for the determined mass filtering steps maintaining the same configuration of the pairs of opposing electrodes to which the attractive DC voltage and the repulsive DC voltage are applied. The width of the selected mass range may change by not more than 10% when the ion transmission efficiency mass filter falls by 50% or more due to the build-up of contamination on the electrodes.