Collision Cell Ion Trapping for Polyatomic Interference Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current mass spectrometry techniques face challenges in effectively suppressing polyatomic interferences, particularly in inductively coupled plasma mass spectrometry (ICP-MS), which hinder trace elemental analysis by drastically affecting detection limits and causing significant signal interference.
Innovation Solution
A method involving a collision cell with a combination of RF and DC electric fields, along with a counterflow gas, is used to radially confine and separate ions based on their collisional cross sections, allowing for the trapping and release of desired ions while rejecting interfering polyatomic ions, thereby enhancing the separation of monatomic analytes from polyatomic interferences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If Kinetic Energy Discrimination (KED) is used to suppress interferences, then interference signals are reduced, but analyte signal loss increases drastically (up to an order of magnitude for higher m/z and more than three orders of magnitude for lower m/z)
Solution Approach 1:
The patent changes the operating parameters of the collision cell by applying a negative DC voltage to the exit aperture electrode, creating a potential well that traps ions. This allows selective suppression of interferences through controlled ion trapping and release cycles, avoiding the drastic analyte signal loss associated with KED while still achieving interference reduction
Solution Approach 2:
The patent implements periodic trapping and release cycles where ions are trapped during a first time period and released during a second time period. This periodic operation allows selective suppression of polyatomic interferences while maintaining analyte signal, resolving the contradiction between interference reduction and signal preservation
2Difficulty of detecting and measuring
If ion selection is employed prior to the collision cell operating in KED mode, then specific ions are selected, but analytical losses increase even greater due to removal of space charge component
Solution Approach 1:
The patent uses the collision cell with trapped ion storage as an intermediary between ion selection and detection. The trapped ions accumulate and are released in controlled cycles, allowing space charge effects to be maintained while still achieving ion selection, thus reducing analytical losses compared to direct KED operation
3Measurement precision
If a gas flow is introduced to separate ions by collisional cross sections, then separation efficiency improves, but kinetic energy of ions is reduced and transmission may be affected
Solution Approach 1:
The patent applies a negative DC voltage to the exit aperture electrode before ions reach it, creating a potential well that预先 traps ions. This preliminary action allows ions to lose kinetic energy through gas collisions without affecting transmission, as the trapped ions are later released by changing the voltage, thus resolving the contradiction between separation efficiency and energy loss
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 significantly reduces polyatomic interference signals, improving the detection of analytes by suppressing unwanted ions and mitigating space charge effects, resulting in enhanced analytical accuracy and reliability.
Implementation Method 1
producing in the collision cell a gas flow which is, at least near the entrance aperture, contrary to the forward axial direction, so as to separate ions in dependence on their collisional cross sections
Implementation Method 2
producing, during a first time period and using the at least one DC exit electrode, a first DC electric field distribution for trapping ions in the collision cell
Implementation Method 3
producing, using the at least one pair of RF axial electrodes, an RF electric field distribution for radially confining the ions
Implementation Method 4
producing, during a second time period and using the at least one DC exit electrode, a second DC electric field distribution for releasing trapped ions in the forward axial direction towards the exit aperture
Data Source
AI summary
A method of operating a collision cell (10) in a mass spectrometer is disclosed. The collision cell comprises an entrance aperture (116), an exit aperture (117) and electrodes (113, 114) for producing electric fields. The method comprises feeding ions in a forward axial direction (LD) through the entrance aperture into the collision cell, producing a first electric field to trap ions, and subsequently producing a second electric field to accelerate trapped ions in the forward axial direction. The method further comprises producing a gas flow (G1) which is, at least at the entrance aperture (116) of the collision cell, contrary to the forward axial direction (LD), so as to reduce the kinetic energy of ions in dependence on their collisional cross sections. A collision cell arranged for carrying out the method is also disclosed, as well as a mass spectrometer comprising such a collision cell.