Mass Spectrometer Collision Cell Potential Control
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Solution Overview
Problem
In ICP-MS, interfering ions generated inside the collision cell cause background noise and reduced measurement sensitivity, even with without-gas analysis, due to their formation from molecules adhering to the cell walls or neutral molecules entering with analyte ions.
Innovation Solution
A mass spectrometer configuration with an ionization chamber, collision cell, mass separation unit, energy barrier unit, and voltage application system, where the ionization chamber has the highest potential, the collision cell the lowest, and the energy barrier unit a potential between the two, facilitating ion acceleration and deceleration to block interfering ions, and optionally using gas in the collision cell for kinetic energy discrimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mass spectrometry unit with enhanced mass resolution is used to separate analyte ions from interfering ions, then the mass peaks can be separated, but the device becomes expensive and increases in size
Solution Approach 1:
A collision cell filled with reaction gas is introduced as an intermediary component between the ionization chamber and the mass spectrometry unit. The reaction gas mediates the separation process by causing interfering ions to undergo chemical reactions that change their mass-to-charge ratio, while analyte ions remain largely unaffected. This allows separation using a standard-resolution mass spectrometry unit, avoiding the need for expensive high-resolution instruments.
Solution Approach 2:
The invention changes the mass-to-charge ratio parameter of interfering ions through chemical reactions with the reaction gas in the collision cell. By controlling the type and pressure of the reaction gas, the mass spectrum of interfering ions is modified, causing their peaks to shift away from analyte ion peaks. This parameter transformation enables effective separation without requiring high mass resolution in the detector.
2Object-generated harmful factors
If a collision cell with reaction gas is used to remove interfering ions, then interfering ions are reduced, but measurement sensitivity decreases due to background noise from interfering ions generated inside the collision cell
Solution Approach 1:
Different regions of the collision cell are assigned different potentials to create localized electric field conditions. The first region (upstream) has a potential that promotes reaction between interfering ions and reaction gas, while the second region (downstream) has a different potential that suppresses further reactions and minimizes background noise generation. This spatial differentiation of electric field properties allows selective removal of interfering ions while protecting measurement sensitivity.
Solution Approach 2:
The collision cell is divided into multiple regions with different electric potentials, creating distinct functional zones. The upstream region focuses on interfering ion removal through enhanced reaction conditions, while the downstream region maintains favorable conditions for analyte ion detection. This segmentation allows independent optimization of each region's function, achieving both interfering ion reduction and sensitivity preservation.
3Object-generated harmful factors
If gas is introduced into the collision cell for kinetic energy discrimination, then interfering ions are blocked, but analyte ions with small mass lose kinetic energy and measurement sensitivity decreases
Solution Approach 1:
The electric potential in the collision cell is made dynamic and spatially variable, creating different kinetic energy conditions in different regions. The upstream region has higher gas pressure and favorable potentials for kinetic energy discrimination of interfering ions, while the downstream region has optimized conditions that preserve analyte ion kinetic energy. This dynamic spatial variation allows selective treatment of different ion types based on their mass and kinetic energy characteristics.
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 configuration effectively reduces the influence of interfering ions generated inside the collision cell, enhancing measurement sensitivity by blocking interfering ions and improving signal-to-noise ratio.
Implementation Method 1
When a high-frequency current flows through the high-frequency induction coil of the plasma torch while a plasma gas (mainly argon gas) passes through the plasma gas tube, a plasma (plasma of as high as 6,000 to 10,000 K) is generated at the tip of the plasma torch.
Implementation Method 2
When a nebulized liquid sample is introduced into the sample gas tube in this state, compounds in the sample are atomized and ionized in the high-temperature plasma, resulting in the generation of atomic ions.
Implementation Method 3
the ionization chamber has the highest potential, the collision cell the lowest, and the energy barrier unit a potential between the two, facilitating ion acceleration and deceleration to block interfering ions
Data Source
AI summary
A mass spectrometer including: an ionization chamber (11) that generates ions from a sample, a collision cell (222) located downstream from the ionization chamber (11), a mass separation unit (2412) located downstream from the collision cell (222), an energy barrier unit (223) located between the collision cell (222) and the mass separation unit (2412), a voltage application unit (30) that applies a voltage to each of the ionization chamber (11), the collision cell (222), and the energy barrier unit (223), and a control unit (42) that controls the voltage application unit (30) such that a potential of the ionization chamber (11) is set to a first potential, a potential of the collision cell (222) is set to a second potential that is lower than the first potential, and a potential of the energy barrier unit (223) is set to a third potential between the first potential and the second potential.