Switchable Ion Guide for Interference-Free Isotope Ratio Analysis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multi-collector isotope ratio mass spectrometry (IRMS) systems face challenges with elemental and molecular interferences, which limit precision and accuracy in isotope ratio measurements. These interferences can arise from sample preparation, contamination, or within the mass spectrometer itself.
Innovation Solution
The ion optical arrangement for a mass spectrometer includes a collision cell that can be switched between a pressurized mode with RF electric focusing and a non-pressurized mode with static electric focusing. This arrangement allows for precise control of ion beam energy and minimizes the noding effect, thereby reducing interference and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a collision cell is pressurized with collision gas to remove chemical interferences, then measurement accuracy is improved, but the noding effect and mass-dependent trajectory variations worsen
Solution Approach 1:
The patent applies dynamics by making the ion guide structure adjustable between different operational configurations. The ion guide can be dynamically reconfigured to provide either RF-only mode for collision cell operation or combined RF+DC mode for field-free transport, allowing the system to adapt its focusing characteristics based on whether the collision cell is pressurized or evacuated
Solution Approach 2:
The patent changes the electrical field parameters by superimposing a DC electric field component onto the existing RF field in the ion guide. This parameter modification alters the ion trajectories to compensate for mass-dependent variations caused by the noding effect, while maintaining the benefits of collision cell operation
2Productivity
If RF fields are used to guide ions through the collision cell, then ion transmission is improved, but mass-dependent trajectory variations and noding effect worsen
Solution Approach 1:
The system dynamically switches between RF-only operation and combined RF+DC operation. During collision cell operation, both RF and DC fields are applied to maintain high transmission. When the collision cell is evacuated, the system can use RF-only mode or reduced DC field to minimize noding effects, optimizing performance for different operational states
Solution Approach 2:
The DC field strength is adjusted as a controllable parameter to optimize the balance between ion transmission and minimization of mass-dependent trajectory variations. The field strength can be tuned based on whether the collision cell is pressurized or evacuated
3Measurement precision
If the collision cell is evacuated to avoid noding effects, then measurement accuracy is improved, but the ability to remove chemical interferences is lost
Solution Approach 1:
The system employs periodic switching between pressurized and evacuated collision cell modes, or between different field configurations (RF-only vs. RF+DC), to alternately address chemical interference removal and noding effect minimization. This periodic action allows both requirements to be satisfied at different times in the measurement cycle
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 solution enables high-resolution, interference-free isotope ratio measurements by maintaining ion beam focus in both pressurized and non-pressurized modes, thereby enhancing the precision and accuracy of isotope ratio analysis.
Implementation Method 1
by kinetic energy discrimination, taking advantage of different cross sections of molecular and elemental species inside the pressurized collision cell which results in different kinetic energy losses of molecular and elemental ions
Implementation Method 2
The collision cell usually comprises a multipole ion guide which is powered by RF fields to guide the ions through the collision cell
Implementation Method 3
a static electric focusing field in the second operation mode
Data Source
AI summary
An ion optical arrangement (1) for use in a mass spectrometer comprises a collision cell defining an ion optical axis along which ions may pass, electrodes comprising a set of parallel poles (11A, 11B, 11C) arranged in the collision cell, and a voltage source for providing voltages to the electrodes to produce electric fields. The ion optical arrangement is arranged for switching between a first operation mode in which the collision cell is pressurized and a second operation mode in which the collision cell is substantially evacuated. The ion optical arrangement is further arranged for producing a radio frequency electric focusing field in the first operation mode and a static electric focusing field in the second operation mode.