Quadrupole Mass Filter Frequency Variation for Resolution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional quadrupole mass spectrometers face challenges in maintaining high sensitivity and mass resolving power when using broad-stability techniques, as controlling the number of oscillatory field cycles experienced by ions is difficult, leading to operational problems at high and low masses.
Innovation Solution
The system adjusts the AC frequency of the AC voltage applied to the quadrupole mass filter while maintaining a constant number of AC cycles per mass, allowing for a broader mass range by varying the frequency for low and high masses, thus avoiding the need for excessively wide variations in other parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of AC cycles per mass is controlled to be constant during a scan, then sensitivity and mass resolving power are improved, but the mass range is limited due to operational problems at high and low masses
Solution Approach 1:
The patent applies dynamics by making the AC frequency variable rather than fixed. The AC frequency is dynamically adjusted during the mass scan to compensate for changes in ion velocity and flight time across the mass range. This allows the system to maintain a constant number of AC cycles per mass while extending the operational mass range, resolving the contradiction between measurement precision and adaptability.
2Ease of operation
If the AC frequency is kept constant during a scan, then the system operation is simplified, but the number of AC cycles per mass varies leading to reduced sensitivity and resolution
Solution Approach 1:
The patent applies parameter changes by modifying the AC frequency parameter during the scan based on the detected mass. The system calculates the required AC frequency to maintain a constant number of cycles per mass and adjusts the frequency accordingly. This dynamic parameter adjustment maintains both ease of operation through automated control and high measurement precision through consistent cycle counting.
3Measurement precision
If the AC frequency is varied to maintain constant AC cycles per mass, then sensitivity and resolution are improved, but the system complexity increases
Solution Approach 1:
The patent applies feedback by using the detected mass information to control the AC frequency. The system continuously monitors the mass being scanned and adjusts the AC frequency in real-time to maintain the optimal number of cycles per mass. This feedback mechanism automates the frequency adjustment process, improving sensitivity and resolution while managing system complexity through intelligent control.
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 enhances mass-invariant RF cycle counts and extends the mass range without operational limitations, improving sensitivity and resolution while maintaining stability across different masses.
Implementation Method 1
by applying fixed and/or ramped AC and DC voltages to configured cylindrical orhyperbolic electrode rod pairs, desired electrical fields stabilize the motion of predetermined ions in the x and y dimensions
Implementation Method 2
The stability range can be varied over time in a scan, thereby providing a mass spectrum over the scanned mass range
Data Source
AI summary
Techniques are provided for scanning frequency and voltages of a multipole mass filter while maintaining substantially the same number of AC cycles per mass during a scan across a range of masses. For example, a mass spectrum can be obtained by controlling a DC axial voltage that accelerates ions into a mass filter, a DC resolving voltage applied to the mass filter, an AC voltage amplitude applied to the mass filter, and an AC frequency of the AC voltage. The settings can be controlled such that ions of different mass-to-charge ratios are within the mass filter for substantially a same number of AC cycles. To achieve the same number of AC cycles, the AC frequency is changed during the scan. For low masses, a higher AC frequency can be used. For high masses, a lower AC frequency can be used.