Quadrupole Electrode Harmonics for Ion Transmission
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Solution Overview
Problem
Quadrupole mass filters face limitations in mass analysis due to distortions in the quadrupole field, leading to inefficient ion transmission and resolution, particularly when higher order harmonics from manufacturing errors or round rod constructions degrade performance.
Innovation Solution
A quadrupole electrode system with added higher multipole harmonics, such as hexapole and octopole fields, is generated by adjusting the geometry of the rods, including rotating Y rods towards X rods and varying their diameters, to create a two-dimensional quadrupole field with controlled harmonics, ensuring stable ion trajectories for specific mass-to-charge ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If round rods are used to construct the quadrupole, then manufacturing is easier, but the quadrupole field becomes distorted and mass resolution deteriorates
Solution Approach 1:
The patent converts the harmful field distortion caused by round rods into a beneficial feature by deliberately introducing higher order multipole harmonics (hexapole, octopole) through controlled geometric modifications. The round rods are rotated by specific angles and/or have different diameters to generate these harmonics, which improve ion transmission and peak shape, thereby converting the manufacturing simplicity of round rods into a advantage while compensating for the field distortion.
2Measurement precision
If higher order multipole harmonics are added to the quadrupole field, then ion transmission and mass resolution are improved, but the device complexity increases
Solution Approach 1:
The patent achieves the addition of higher order multipole harmonics by changing geometric parameters of the existing quadrupole rods rather than adding new components. Specifically, it modifies the rotation angles and/or diameters of the rods, which are simple parameter adjustments that generate the desired hexapole and octopole fields without increasing device complexity.
3Manufacturing precision
If the quadrupole field is optimized for ideal hyperbolic rods, then field accuracy is improved, but manufacturing precision requirements increase
Solution Approach 1:
Instead of using ideal hyperbolic rods that are difficult to manufacture, the patent inverts the approach by using simple round rods and deliberately introducing controlled geometric imperfections (rotation and diameter variations) to generate the desired higher order harmonics. This inversion transforms the manufacturing challenge into a solution, where the 'imperfections' are actually controlled features that improve performance.
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 ion transmission and mass resolution by optimizing the quadrupole field harmonics, improving MS/MS efficiency and peak shape while maintaining the capability to operate as a mass filter at low pressures.
Implementation Method 1
a quadrupole electrode system for connection to a voltage supply means for providing an at least partially-AC potential difference within the quadrupole electrode system... to generate a two-dimensional substantially quadrupole field
Implementation Method 2
having a quadrupole harmonic with amplitude A2 and a hexapole harmonic with amplitude A3... A3 is greater than 0.1% of A2
Implementation Method 3
an octopole harmonic with amplitude A4 wherein the magnitude of A4 is less than 0.1% of the magnitude of A2
Implementation Method 4
providing an at least partially-AC potential difference within the quadrupole electrode system... V(t)=+(U−Vrf cos Ωt)
Implementation Method 5
U is a DC voltage, pole to ground... combinations of a and q which give stable ion motion
Implementation Method 6
an ion source for injecting ions substantially centered along a field centre of the two-dimensional substantially quadrupole field
Implementation Method 7
a dipole potential of the two-dimensional substantially quadrupole field is lower along the field centre than along the quadrupole axis
Data Source
AI summary
A mass spectrometer and a method of operating and building same is provided in which a hexapole component is deliberately added to a substantially quadrupole field. This can result in unwanted octopole and dipole fields also being added to the substantially quadrupole field. Modifications to the mass spectrometer as well as ways of operating the mass spectrometer are provided for dealing with the unwanted octopole and dipole fields.