Quadrupole Mass Filter Frequency Amplitude Scan
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Solution Overview
Problem
Quadrupole mass filters (QMFs) are limited in detecting high m/z ions due to electrical breakdown and power consumption concerns, and their resolving power suffers when trying to scan frequency over a wide range, as commercial frequency synthesizers lack the necessary accuracy.
Innovation Solution
A method involving a quadrupole mass filter that applies a series of AC voltages with distinct frequencies and adjusted amplitudes to separate ions, allowing for increased m/z values to be detected while maintaining resolving power, by using a synchronized frequency and amplitude scan, and employing trapezoidal waveforms to minimize harmonic contributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If RF amplitude is increased to detect higher m/z values, then the maximum detectable m/z value increases, but electrical breakdown and power consumption become concerns
Solution Approach 1:
The patent changes the operating parameters by using frequency modulation instead of amplitude modulation. Specifically, it varies the frequency of the RF signal across a wide range (e.g., 100 kHz to 10 MHz) while maintaining moderate amplitude levels, thereby achieving high m/z detection without the harmful effects of high amplitude operation
Solution Approach 2:
The patent transitions from the traditional one-dimensional amplitude scanning approach to a two-dimensional approach by introducing frequency as an additional dimension. This frequency-amplitude matrix method allows the system to access different m/z ranges through frequency variation while using amplitude only for fine-tuning transmission
2Quantity of substance
If frequency is decreased to increase detectable m/z values, then the maximum m/z value increases, but resolving power suffers due to poor frequency definition
Solution Approach 1:
The patent employs dynamic frequency modulation where the RF frequency is continuously varied over a wide range during the scanning process. This dynamic approach allows the system to maintain good frequency definition at each measurement point while covering a broad m/z range, thereby preserving resolving power across the entire spectrum
Solution Approach 2:
The system uses feedback mechanisms to precisely control and define the RF frequency at each step of the scan. By monitoring and adjusting the frequency in real-time based on the desired m/z target, the system maintains sharp frequency definition even when operating at low frequencies required for high m/z detection
3Adaptability or versatility
If frequency is scanned over a wide range to detect large m/z values, then the detectable m/z range increases, but accuracy is insufficient with commercial frequency synthesizers
Solution Approach 1:
The patent segments the wide frequency scanning range into multiple discrete, precisely controlled steps. Rather than attempting to scan the entire range continuously with a single synthesizer, the system divides the frequency spectrum into manageable segments, each accurately generated and measured, thereby maintaining high frequency accuracy across the full detectable range
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 enables the detection of higher m/z values with improved resolving power and transmission efficiency, effectively expanding the useful range of QMFs without substantial decreases in transmission efficiency.
Implementation Method 1
applying a plurality of AC voltages to the quadrupole to separate the ions
Data Source
AI summary
A quadrupole mass filter and method for operating the filter are described. Sample ions, each having a mass-to-charge ratio, are passed to a quadrupole at least one AC voltage is applied thereto to separate the ions by incrementally varying a frequency of the at least one AC voltage within a first range of frequencies and, for each of at least some of the incremental frequencies in the first range of frequencies, incrementally varying an amplitude of the at least one AC voltage within a range of amplitudes, wherein each incremental frequency and incremental amplitude pair of the at least one AC voltage creates a different band pass filter in the quadrupole through which produced ions having a different corresponding mass-to-charge ratio pass to a detector.