IMS-MS Interface Ion Funnel Multipole Guide
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Solution Overview
Problem
Existing interfaces between ion mobility spectrometry (IMS) and time-of-flight mass spectrometry (TOF MS) systems compromise IMS resolution and ion transmission due to segmented quadrupole ion guides and complex instrument design.
Innovation Solution
A novel interface system featuring a first ion guide connected to a second ion guide at a lower pressure, with an ion funnel and multipole ion guides generating radial RF and axial DC fields, optimized to maintain IMS resolution and ion transmission by controlling pressure stages and electric fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If segmented quadrupole ion guides with multiple differentially pumped pressure regions are used to interface IMS and TOF MS, then ion transmission can be maintained, but IMS resolution deteriorates and device complexity increases
Solution Approach 1:
The interface is divided into multiple pressure regions (first pressure region for IMS, second pressure region for TOF MS) separated by a skimmer interface. This segmentation allows each region to be optimized independently - the IMS region maintains higher pressure for good resolution while the TOF MS region operates at lower pressure, with the skimmer acting as a conductance-limiting aperture that enables pressure differential while transmitting ions.
Solution Approach 2:
The skimmer interface acts as an intermediary component between the IMS drift cell and the TOF MS. It is a conductance-limiting aperture that couples the two pressure regions, allowing ions to pass from the higher pressure IMS region to the lower pressure TOF MS region while maintaining the pressure differential needed for both instruments to function optimally.
2Quantity of substance
If segmented quadrupole ion guides with multiple differentially pumped pressure regions are used to interface IMS and TOF MS, then ion transmission can be maintained, but device complexity increases
Solution Approach 1:
The patent combines multiple functions into the skimmer interface component: it serves as both a pressure differential barrier and an ion transmission aperture. Additionally, the RF-only hexapole ion guide is positioned to perform both ion guiding and focusing functions. This merging reduces the number of separate components needed compared to using segmented quadrupole guides with multiple independent pumping regions.
3Quantity of substance
If RF-only hexapole ion guides are used in the interface, then ion transmission can be maintained, but IMS resolution deteriorates
Solution Approach 1:
The RF-only hexapole ion guide uses radio frequency voltage applied to six electrodes arranged in a hexagonal pattern around the ion beam path. This creates a time-varying pseudo-potential well that confines ions radially while allowing axial transmission. The periodic RF action provides ion guidance and focusing without the mass filtering effects of quadrupole guides, thus maintaining IMS resolution while enabling ion transmission through the interface.
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
The interface system enhances IMS resolution and ion transmission while minimizing ion fragmentation, allowing for improved analysis of complex chemical mixtures by preserving the IMS separation and mass resolution.
Implementation Method 1
an ion funnel in the first chamber, the ion funnel surrounding a funnel interior and configured for generating a radial RF ion confining field in the funnel interior
Implementation Method 2
a multipole ion guide in the second chamber, the ion guide comprising a plurality of guide electrodes elongated along the axis, circumferentially spaced about the axis, and surrounding a guide interior, the guide electrodes configured for generating a radial RF ion confining field in the guide interior and an axial DC gradient along a length of the ion guide
Implementation Method 3
The ions are produced from a sample in an ion source and travel through the drift cell under the influence of a DC voltage gradient. During this travel, the ions become separated based on their different collision cross-sections, which can be correlated to their differing mobilities through the drift gas.
Implementation Method 4
an IMS system may be coupled with a time-of-flight (TOF) MS system that provides fast, high-resolution mass analysis. In the combined IMS-TOF MS system, ions are separated by mobility prior to being transmitted into the TOF MS where they are mass-resolved based on their flight times to the detector.
Data Source
AI summary
An interface for an ion mobility spectrometry-mass spectrometry (IMS-MS) system includes a first ion guide for receiving ions from an IMS drift cell, and a second ion guide for receiving ions from the first ion guide, and positioned in a chamber separate from the first ion guide. Electrodes of the second ion guide subject the ions to an axial DC electric field while the second ion guide is held at a lower pressure than the first ion guide. In some embodiments, the first ion guide may be an ion funnel and the second ion guide may be a linear multipole device.