Ion Mobility Spectrometer Continuous Ion Beam Duty Cycle
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Solution Overview
Problem
Conventional ion mobility spectrometry techniques face challenges with low duty cycle efficiency and signal distortion due to high ion flux and space-charge effects, particularly in sub-atmospheric RF confined IMS devices, and require complex modulation and synchronization of ion gates and detectors.
Innovation Solution
The method involves modulating the introduction of ions into an ion mobility separator with a first frequency and varying it over time, while recording and processing the ion signal with a Time of Flight mass analyser at a higher acquisition rate, allowing for continuous ion beam operation and reducing the need for ion trapping, thus enhancing duty cycle and reducing contamination and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ions are accumulated in an ion trapping region to improve duty cycle, then duty cycle increases, but space-charge effects cause signal loss and drift time distortions
Solution Approach 1:
The patent implements continuous ion beam operation through a single ion gate that remains open throughout the IMS separation cycle, eliminating the need for ion accumulation and trapping. This continuous transmission maintains constant ion flux without space-charge effects, achieving high duty cycle (near 100%) while preserving signal quality and drift time accuracy.
Solution Approach 2:
The patent removes the ion trapping region and accumulation cavity from the instrument design, extracting the problematic component that causes space-charge effects. By eliminating the need for ion storage, the system avoids signal loss and drift time distortions while maintaining high productivity through continuous ion transmission.
2Ease of operation
If conventional gating is used with identical frequencies on both ion gates, then synchronization is simplified, but duty cycle is limited to 25%
Solution Approach 1:
The patent removes the second ion gate from the system, eliminating the need for complex gating synchronization between two gates. With only a single ion gate at the entrance, the system achieves simplified operation while dramatically improving duty cycle to near 100% through continuous ion transmission throughout the drift period.
Solution Approach 2:
Instead of using two gates with identical gating frequencies to achieve 25% duty cycle, the patent inverts the approach by using a single gate that remains open continuously, allowing ions to enter the drift region without periodic interruption, thereby achieving near 100% duty cycle with simplified gating control.
3Measurement precision
If a second ion gate is used at the exit of the IMS device, then ion mobility separation can be achieved, but device complexity increases
Solution Approach 1:
The patent removes the second ion gate from the instrument, reducing the device from a dual-gate configuration to a single-gate system. Ion mobility separation is achieved through the drift region itself, with ions separated by their drift times detected by a standard mass spectrometer detector, eliminating the need for a second gate while maintaining measurement precision.
Solution Approach 2:
The patent uses the drift region gas and electric field as an intermediary medium to achieve ion mobility separation without requiring a second ion gate. The drift region acts as the separating element, with ions naturally separating based on their mobility characteristics during flight through the drift region, detected subsequently by the mass spectrometer.
4Productivity
If ion flux towards the IMS device is high, then productivity increases, but charge density becomes high causing space-charge effects
Solution Approach 1:
The patent implements continuous ion beam transmission without accumulation or trapping, maintaining constant but moderate ion flux throughout the drift region. This continuous flow prevents charge density buildup that causes space-charge effects, while still achieving high productivity through near 100% duty cycle operation and efficient ion transmission.
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 improves ion mobility spectrometry by increasing duty cycle, reducing contamination, and providing high-quality mobility spectra with precise ion mobility measurements, while simplifying the instrument design and reducing data processing burdens.
Implementation Method 1
detecting ions that have exited the ion mobility separator with a detector of a time of flight mass analyser
Implementation Method 2
separating the ions that enter the ion mobility separator according to ion mobility
Data Source
AI summary
A method of ion mobility spectrometry is disclosed comprising: transmitting a plurality of ions to an ion mobility separator 6; modulating the introduction of the ions into the ion mobility separator 6 at a first modulation frequency; separating the ions that enter the ion mobility separator 6 according to ion mobility; detecting ions that have exited the ion mobility separator with a detector of a time of flight mass analyser 8; varying the first modulation frequency with time; recording the intensity of the ion signal output from the detector to produce recorded data; modulating the recorded data as a function of the time that the data was recorded and at a second modulation frequency, wherein the second modulation frequency is varied as a function of the time that the data was recorded; and determining, from the variation in intensity of the ion signal in the modulated data as a function of the second modulation frequency, the ion mobilities of the ions that have been detected.