Differential Mobility Analyzer Focusing Ion Inlet
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Solution Overview
Problem
Current ion-selecting devices face challenges in detecting and quantifying explosives at low concentrations due to prominent background signals from interfering chemical compounds, leading to false positives, and require high-resolution ion selection which is often achieved by increasing sheath gas flow rates, resulting in turbulence and high costs.
Innovation Solution
A differential mobility analyser apparatus with a focusing ion inlet that narrows ion trajectories using a non-uniform electric field, allowing ions of specific mobility to be selected without increasing sheath gas flow rates, thereby enhancing resolution without turbulence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sheath gas flow rate is increased to improve ion selection resolution, then resolution is improved, but turbulence occurs and costs increase
Solution Approach 1:
The device is divided into two functional chambers: a first chamber for ion separation and a second chamber for ion detection. This segmentation allows the sheath gas flow to be optimized for resolution in the first chamber without creating turbulence that would affect the entire system, as the chambers are spatially separated and connected via a controlled aperture.
Solution Approach 2:
A focused ion beam is used as an intermediary between the ion separation chamber and the detection chamber. The ions are focused into a narrow beam through a focal point, allowing precise ion selection to be transmitted through a small aperture without requiring high sheath gas flow rates that would cause turbulence in the detection chamber.
2Measurement precision
If sheath gas flow rate is increased to improve ion selection resolution, then resolution is improved, but device complexity and cost increase
Solution Approach 1:
The device is divided into two functional chambers: a first chamber for ion separation and a second chamber for ion detection. This segmentation allows the sheath gas flow to be optimized for resolution in the first chamber without creating turbulence that would affect the entire system, as the chambers are spatially separated and connected via a controlled aperture.
Solution Approach 2:
The invention changes the operational parameters by using a focused ion beam with specific angular divergence and a controlled aperture size. This allows high-resolution ion selection to be achieved without requiring proportionally higher sheath gas flow rates, thereby reducing the complexity and cost associated with high-flow gas handling systems.
3Measurement precision
If background signals from interfering compounds are reduced to improve detection accuracy, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The device is divided into two functional chambers: a first chamber for ion separation and a second chamber for ion detection. This segmentation allows the sheath gas flow to be optimized for resolution in the first chamber without creating turbulence that would affect the entire system, as the chambers are spatially separated and connected via a controlled aperture.
Solution Approach 2:
The invention extracts only the ions of interest from the complex mixture by using ion mobility separation in the first chamber. The focused ion beam technique extracts specific ion trajectories while excluding interfering compounds, allowing background signals to be reduced without requiring complex additional filtering or analysis systems.
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 solution enables higher resolution and sensitivity in detecting ions of specific mobility, reducing the need for high sheath gas flow rates, leading to a more compact, cost-effective, and efficient ion-selecting device.
Implementation Method 1
separating and collecting ions of a predetermined ion mobility from a gaseous mixture of ions of different ion mobilities
Implementation Method 2
two or more electrodes arranged to provide an ion-separating electric field across the ion-separation chamber
Implementation Method 3
a focusing zone is provided in the focusing chamber, the focusing zone comprising at least two surfaces where a non-uniform density of electric charge can be created; subjecting the ion cloud in the sample gas in the focusing zone to a non-uniform electric field generated by the non-uniform density of electric charge such that the electric field modifies ion trajectories in the sample gas so that they converge
Implementation Method 4
introducing a stream of sheath gas through the sheath gas inlet at a predetermined flow rate; directing the stream of sample gas containing the ion stream of reduced width from the focusing chamber through the sample gas flow inlet into the ion-separation chamber
Data Source
AI summary
The invention provides a method of separating and collecting ions of a predetermined ion mobility from a gaseous mixture of ions of different ion mobilities using a differential mobility analyser apparatus, wherein the differential mobility analyser apparatus comprises an ion-separation chamber having:(a) a sample gas flow inlet;(b) a focusing chamber, an opening at one end of which serves as the sample gas flow inlet through which sample gas can flow into the ion-separation chamber;(c) a sheath gas inlet connected or connectable to a supply of sheath gas;(d) a sheath gas outlet;(e) an ion outlet through which the ions of predetermined ion mobility can be collected; and(f) two or more electrodes arranged to provide an ion-separating electric field across the ion-separation chamber;wherein the focusing chamber is oriented at an angle of from 30° to 90° relative to a direction of flow of the sheath gas along the ion-separation chamber;and wherein a focusing zone is provided in the focusing chamber, the focusing zone comprising at least two surfaces where a non-uniform density of electric charge can be created;the method of separating and collecting ions of predetermined ion mobility comprising:(i) introducing a stream of sheath gas through the sheath gas inlet at a predetermined flow rate;(ii) introducing a stream of sample gas containing an ion cloud into and through the focusing chamber and through the focusing zone therein at a predetermined flow rate;(iii) subjecting the ion cloud in the sample gas in the focusing zone to a non-uniform electric field generated by the non-uniform density of electric charge such that the electric field modifies ion trajectories in the sample gas so that they converge to produce an ion stream of reduced width;(iii) directing the stream of sample gas containing the ion stream of reduced width from the focusing chamber through the sample gas flow inlet into the ion-separation chamber; and(iv) selecting a field strength for the ion-separating electric field so as to attract ions of a predetermined ion mobility to the ion outlet.Also provided is differential mobility analyser apparatus for separating and collecting ions of a predetermined ion mobility from a gaseous mixture of ions of different ion mobilities using a differential mobility analyser apparatus, wherein the differential mobility analyser apparatus comprises an ion-separation chamber having:(a) a focusing chamber connected or connectable to a supply of sample gas containing ions of interest;(b) a sheath gas inlet connected or connectable to a supply of sheath gas;(b) a sheath gas outlet;(c) an ion outlet through which the ions of predetermined ion mobility can be quantified or collected; and(d) two or more electrodes arranged to provide an ion-separating electric field across the ion-separation chamber;wherein the sample gas inlet is oriented at an angle of from 30° to 90° relative to a direction of flow of the sheath gas along the ion-separation chamber;and wherein the apparatus is configured to provide a focusing zone in the focusing chamber, the focusing zone comprising at least two surfaces where a non-uniform density of electric charge is created so as to generate a non-uniform electric field that modifies ion trajectories in a sample gas passing through the focusing chamber and through the focusing zone so that they converge to produce an ion stream of reduced width;the apparatus comprising a controller that enables the ion-separating electric field to be varied to attract ions of a predetermined ion mobility to the ion outlet.