Ion Mobility Spectrometer with Segmented Electric Field for Enrichment
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Solution Overview
Problem
Current ion mobility spectrometers face limitations in sensitivity and selectivity for ion enrichment and detection, particularly in high flow conditions, leading to instability and reduced sample throughput, and existing methods either fail to achieve enrichment or compromise resolution and efficiency.
Innovation Solution
A device with a gas tube and multiple electrodes under ambient or low vacuum conditions, where ions are balanced by opposing electric fields and gas flow velocities, allowing for selective ion enrichment and detection by accumulating ions with specific mobility in specific regions, enhancing sensitivity and resolution through adjustable electric field distributions and radial focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional ion mobility spectrometer uses dc axial electric field for ion separation, then ion separation is achieved, but sensitivity and enrichment capability are limited
Solution Approach 1:
The device segments the drift tube into multiple regions with different electric field strengths (high field region and low field region), allowing differential mobility separation while maintaining overall ion accumulation. This segmentation enables both resolution and enrichment by creating distinct separation zones within the overall drift path.
Solution Approach 2:
Different regions of the drift tube are assigned different electric field characteristics - the high field region provides strong separation force for resolution, while the low field region allows ion accumulation for enrichment. This local quality differentiation resolves the contradiction between separation precision and concentration buildup.
2Productivity
If high flow rate is used for sample introduction, then sample throughput increases, but ion enrichment stability decreases
Solution Approach 1:
The electric field strength is made dynamically adjustable across different drift tube regions, allowing the system to adapt to varying flow rates. By dynamically balancing the electric field forces against the gas flow velocity in different zones, the system maintains ion accumulation stability even at high throughput conditions.
3Volume of moving object
If ion mobility spectrometer operates at atmospheric pressure, then device compactness improves, but ion mean free path decreases affecting resolution
Solution Approach 1:
The high field region is positioned at the beginning of the drift tube to perform preliminary separation of ions based on their mobility differences. This preliminary action occurs when ions still have sufficient kinetic energy and separation efficiency, compensating for the shorter overall drift path available at atmospheric pressure.
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 enables efficient ion enrichment and detection, increasing sensitivity and throughput while maintaining spatial resolution, allowing for the detection of trace substances like explosives and illicit drugs with improved selectivity and reduced ion loss.
Implementation Method 1
ions are accelerated by the electric field and collided with neutral gas and reaches its velocity which is proportional to the field strength (v=KE). Here v is the velocity of ion, E is electric field strength, K the ion mobility
Implementation Method 2
The Differential Mobility Spectrometer (DMS), as the second category, makes use of the difference of ion mobility between in the high field and low field, to achieve the separation of ions
Implementation Method 3
A compensation DC voltage, which is normally applied on another parallel electrode, is used to cancel the displacement, to ensure that the ions can flow through the gap between electrodes
Implementation Method 4
Different from the gas chromatography, the compounds to be separated and detected in the ion mobility spectrometer must be ionized, and then under the effect of the electric field in accordance with the molecular size of the ion to be separated
Implementation Method 5
the compounds to be separated and detected in the ion mobility spectrometer must be ionized
Data Source
AI summary
A device for separating, enriching and detecting ions comprises: a gas tube, in which a carrier gas flows at a uniform rate; an ion source; multiple electrodes provided in the gas tube and applied with electric voltages respectively, so that at least an electric field is produced along the axis of the gas tube; an ion detector; and an ion extraction channel, by which specific enriched ions will be guided across the side wall of the gas tube toward the ion detector and be analyzed. The device enriches ions utilizing the following characteristic: compound ions with specific ion mobility maintain a dynamic balance for a period of time in a flow field under the combination of a carrier gas and a suitable electrical field against the direction of the carrier gas. Simultaneously, multiple compound particles with different ion motilities can be separated and enriched at positions with different electrical field intensities in a flow field in the same manner. The device also comprises synchronously export latitudinally enriched ions at different positions in a flow field, and performs later mass analysis using a mass spectrometer.