FT Quadrupole Calibration Using Mathieu q and Secular Frequency
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Solution Overview
Problem
Conventional calibration methods for Fourier Transform (FT) mass spectrometers are complex and difficult to implement due to the non-linear relationship between measured ion secular frequency and m/z ratios, making accurate calibration challenging.
Innovation Solution
A method involving the measurement of secular frequencies of a calibrant ion for various RF voltages applied to the FT mass analyzer, calculation of Mathieu β and q parameters, and determination of offset RF voltage amplitudes to generate a calibration curve, allowing for accurate calculation of m/z ratios of analytes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration methods based on secular frequency of ions within a quadrupole field are used, then calibration can be performed, but the process becomes complicated and difficult to implement due to the non-linear relationship between measured ion secular frequency and m/z ratios
Solution Approach 1:
The patent transforms the calibration approach by changing the mathematical parameters used. Instead of directly using the non-linear secular frequency-m/z relationship, it introduces Mathieu parameters (a and q) as intermediate variables. The calibration curve is constructed in the parameter space (a-q plane) rather than in the direct frequency-m/z space, linearizing the relationship and simplifying the calibration process while maintaining accuracy.
Solution Approach 2:
The patent introduces Mathieu parameters as intermediary variables between the measured secular frequency and the desired m/z ratio. These parameters serve as a bridge that transforms the complex non-linear relationship into a more manageable form, allowing for simplified calibration through the construction of calibration curves in the parameter space rather than directly in frequency space.
2Productivity
If secular frequency scanning is performed in a quadrupole field, then mass analysis can be conducted, but the calibration becomes difficult to implement due to dependence on knowing mass-dependent delays for ion ejection
Solution Approach 1:
The patent changes the operational parameters by working in the Mathieu parameter space rather than directly in frequency space. This transformation allows the system to perform mass analysis through secular frequency scanning while avoiding the need to know mass-dependent delays, as the calibration is performed in the a-q parameter space where such dependencies are eliminated.
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 simplifies the calibration process by generating a calibration curve that enables precise determination of m/z ratios of analytes, improving the accuracy and efficiency of FT mass spectrometer calibration.
Implementation Method 1
The application of radiofrequency (RF) voltages to the rods can provide an electromagnetic field for radial confinement of ions as they pass through the mass analyzer
Implementation Method 2
the measured quantity in the secular frequency of ions within the mass spectrometer (i.e., the characteristic oscillation frequency of an ion in the RF field)
Data Source
AI summary
In one aspect, a method of calibrating a Fourier Transform (FT) multipole mass spectrometer is disclosed, which comprises measuring a plurality of secular frequencies of a calibrant ion in a multipole FT mass analyzer for a plurality of RF voltages (VRF) applied to at least one rod of the multipole mass analyzer, calculating Mathieu β and q parameters for each of 5 the measured secular frequencies, and determining RF voltage amplitude (VRF) for each calculated q parameter. For each calculated q parameter, an offset RF voltage amplitude (ΔVRF) corresponding to a deviation of the applied VRF and the calculated VRF is determined so as to generate a ΔVRFv.s. q calibration curve.