Collision Cell Multipole with Variable Diameter for Ion Transmission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing collision cell multipoles in mass spectrometers face challenges in efficiently transmitting analyte ions while preventing the passage of interfering species, particularly low-mass ions and background ions, which can lead to increased background counts and reduced sensitivity.
Innovation Solution
A collision cell multipole design featuring a plurality of electrodes with varying radial distances along its length, including a high acceptance region at the entrance and a reduced diameter region for ejecting low-mass ions, combined with a changing q value to optimize ion transmission and rejection, and a curved or stepped configuration to minimize pseudo-potential barriers and improve ion trajectories.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional collision cell multipole with uniform diameter is used, then ion transmission is maintained, but interfering low-mass ions and background ions cannot be effectively rejected
Solution Approach 1:
The multipole electrode structure is segmented into distinct regions along its length: an entrance region with larger diameter for high ion acceptance, an intermediate region with reduced diameter for low-mass ion rejection, and an exit region with larger diameter for improved transmission. This spatial segmentation allows different functional zones within a single continuous structure.
Solution Approach 2:
Different sections of the multipole electrode have different local geometries optimized for specific functions. The entrance region provides high acceptance for all ions, the intermediate region creates a low-mass cut-off for interfering ions, and the exit region enhances transmission of selected ions. Each local geometry is tailored to its specific operational requirement.
2Object-affected harmful factors
If a reduced diameter region is introduced to eject low-mass ions, then interfering ions are rejected, but ion transmission may be compromised
Solution Approach 1:
The solution transitions from a one-dimensional uniform diameter to a three-dimensional variable diameter structure. By adding the radial dimension variation along the axial length, the system creates a low-mass cut-off region without completely blocking ion transmission, as ions can still pass through the reduced diameter region with appropriate trajectory control.
Solution Approach 2:
The multipole electrode system uses dynamic RF voltages applied to the electrodes to create time-varying electric fields that dynamically control ion trajectories. This dynamic control allows selective rejection of low-mass ions in the reduced diameter region while maintaining transmission of higher mass analyte ions through the same region.
3Ease of operation
If uniform q value is applied throughout the multipole, then operation is simplified, but ion trajectory control and rejection characteristics are suboptimal
Solution Approach 1:
The q value parameter is segmented into different zones along the multipole length, corresponding to the different geometric regions. The entrance region, intermediate region, and exit region can have different q value settings optimized for their specific functions, rather than using a single uniform q value throughout.
Solution Approach 2:
Different sections of the multipole have locally optimized q values matched to their specific functional requirements. The entrance region uses q values for high acceptance, the intermediate region uses q values for low-mass rejection, and the exit region uses q values for enhanced transmission, creating locally optimized conditions throughout the structure.
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 design enhances ion transmission for low-mass analytes while effectively rejecting interfering ions, reducing background counts and improving sensitivity, particularly for applications like ICP-MS, by providing a high-pass filter characteristic and low-mass cut-off, thereby improving the overall performance of the mass spectrometer.
Implementation Method 1
the multipole is usually operated in the radio frequency (RF)-only mode. Generally speaking, the RF-only field does not separate masses like an analysing quadrupole, but has the effect of focusing and guiding the ions along the multipole axis
Implementation Method 2
The ions collide and react with molecules of the collision/reaction gas and, by various ion-molecule collision and reaction mechanisms, interfering ions are preferentially converted to non-interfering neutral species
Implementation Method 3
The ions collide and react with molecules of the collision/reaction gas and, by various ion-molecule collision and reaction mechanisms, interfering ions are preferentially converted to non-interfering neutral species
Implementation Method 4
A radiofrequency electric current is supplied to the torch coil and the resulting alternating magnetic field causes the free electrons to be accelerated to bring about further ionisation of the plasma gas
Implementation Method 5
This process continues until a steady plasma state is achieved, at temperatures typically between 5,000 K and 10,000 K
Implementation Method 6
the temperature is high enough to cause atomisation and then ionisation of the sample
Data Source
AI summary
Mass spectrometer collision/reaction cell multipole and method. The multipole may have first and second portions and an intermediate portion therebetween, the first and second portions operating at first and second q values lower than a third q value at the intermediate portion. A low-mass cut-off of the multipole may be controlled by varying a q value from a first to at least a second value. The multipole may have multipole electrodes disposed about a central axis and having a respective first portion, second portion, and intermediate portion therebetween which is radially closer to the central axis. This offers relatively high acceptance and ion transmission, while providing low-mass cut-off for removing undesired/interfering ions and helping reduce background count.