Quadrupole Mass Filter Voltage Control for Orthogonal Acceleration Time-of-Flight
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Solution Overview
Problem
In orthogonal acceleration type time-of-flight mass spectrometers, short measurement periods lead to ions with large mass-to-charge ratios from previous periods interfering with those of smaller mass-to-charge ratios, causing inaccurate mass spectra due to overlapping peaks, which complicates data processing and requires repeated measurements.
Innovation Solution
A mass spectrometer configuration with a quadrupole mass filter and voltage generator applying a specific radio-frequency and direct current voltage to create a multipole electrical field, blocking ions with long time-of-flight from passing through, ensuring only ions within the desired mass-to-charge ratio range are detected, thereby preventing interference from previous measurement periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the measurement period is shortened to improve quantitative accuracy, then the measurement time intervals decrease and reproducibility improves, but ions with long time-of-flight from previous periods interfere with current period ions causing peak overlap and inaccurate mass spectra
Solution Approach 1:
The patent applies preliminary action by using the quadrupole mass filter to block ions with large mass-to-charge ratios (long time-of-flight) before they can interfere with the detection of ions from the current measurement period. This preventive measure is implemented in advance at the ion transport stage, ensuring that only ions within the desired mass-to-charge ratio range reach the flight space and detector, thereby eliminating peak overlap and interference effects before they occur.
2Measurement precision
If ions are accelerated in a pulsed fashion orthogonal to the ion beam direction to improve mass resolution, then mass-resolving power increases, but the device complexity increases due to the need for orthogonal accelerator and timing synchronization
Solution Approach 1:
The patent applies universality by making the quadrupole mass filter serve multiple functions: it acts as both an ion guide to transport ions efficiently and as a mass filter to select ions within a specific mass-to-charge ratio range. This multi-functionality eliminates the need for separate ion guide and mass filter components, thereby reducing device complexity while maintaining high mass-resolving power through orthogonal acceleration.
3Productivity
If the quadrupole mass filter is controlled to function as an ion guide with minimal mass separation to improve ion transmission, then ion transmission efficiency increases, but ions with large mass-to-charge ratios are not blocked causing interference in short measurement periods
Solution Approach 1:
The patent applies dynamics by making the mass-to-charge ratio selection range of the quadrupole mass filter adjustable and adaptable to the measurement period. The filter parameters are dynamically optimized to balance ion transmission efficiency with the blocking of ions having large mass-to-charge ratios, ensuring that sufficient ions are transmitted for accurate detection while preventing interference from ions that would exceed the measurement period.
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 allows for accurate mass spectra acquisition without the influence of ions from previous measurement periods, improving quantitative accuracy and reducing the need for complex data processing and repeated measurements.
Implementation Method 1
a voltage generator configured to apply, to the multipole electrode, a voltage obtained by adding a radio-frequency voltage and a direct current voltage, and to apply, to the multipole electrode, a voltage for forming a multipole electrical field in which ions within a range of equal to or larger than a predetermined mass-to-charge ratio
Implementation Method 2
The period of time required for their flight is measured, and the mass-to-charge ratio of each ion is calculated from its time of flight
Implementation Method 3
an orthogonal acceleration type time-of-flight mass spectrometer, which accelerates ions into the flight space in a direction orthogonal to the incident direction of the ion beam
Data Source
AI summary
When a normal mass spectrometry is performed without dissociating an ion, the m/z range limitation voltage setting unit applies a radio-frequency voltage to each rod electrode of the quadrupole mass filter and controls the quadrupole voltage generator so as to apply a direct current voltage smaller than that at the time of ion selection for MS/MS spectrometry. When a small direct current voltage is applied, a mass scanning line is set so as to pass through a stability region on a Mathieu diagram over a long range, hence large m/z ions that do not fall within the stability region are blocked in the quadrupole mass filter. By adjusting a cut-off point on larger m/z side blocked in accordance with the measurement period of OA-TOFMS including the orthogonal accelerator, heavy ions that cause period delay are prevented from being introduced into the orthogonal accelerator.