Ion Mobility Spectrometer Local Ionization Source
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Solution Overview
Problem
Ion mobility spectrometers face challenges in efficiently ionizing samples due to interference from NOx compounds and maintaining consistent physical-chemical properties in the drift medium, leading to measurement errors and contamination issues.
Innovation Solution
An ion mobility spectrometer design with a cylindrical drift chamber and reaction chamber, featuring a sample gas inlet that combines with the drift gas in a unidirectional flow to suppress NOx formation and contamination, and a local ionisation source placed near the gas outlet to enhance ionisation efficiency, along with a method for operating the spectrometer to control NOx compound formation and ion mobility measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional ion mobility spectrometer uses a reaction chamber with sample gas inlet and ionisation source, then ionisation of sample material occurs, but NOx compounds are formed which interfere with measurement and contaminate the drift medium
Solution Approach 1:
The harmful NOx compound formation is extracted and eliminated by removing the traditional reaction chamber configuration. The patent separates the ionisation function from the drift medium path, using a localized ionisation source that ionises sample gas before it enters the drift chamber, preventing NOx formation in the drift medium while maintaining effective ionisation.
Solution Approach 2:
A carrier gas acts as an intermediary medium that transports sample material to the ionisation zone without being contaminated by NOx compounds. The carrier gas flow path is designed to prevent mixing between ionisation products and the drift medium, using the carrier gas as a protective intermediary that delivers samples cleanly to the detection region.
2Stability of the object's composition
If the drift medium is continuously renewed by gas flow, then physical-chemical properties are maintained, but the gas flow can influence effective drift time and introduce contamination
Solution Approach 1:
The gas flow system is segmented into distinct zones: a carrier gas flow for sample transport and a drift gas flow for maintaining drift medium properties. These segmented flows are carefully controlled to prevent mixing that would affect drift time measurements, allowing continuous renewal of the drift medium without compromising measurement precision.
Solution Approach 2:
Different regions of the drift chamber have different gas flow characteristics optimized for their specific functions. The inlet region has higher flow for sample introduction, while the drift region maintains stable, laminar flow for accurate measurements. This local optimization of gas flow properties maintains drift medium homogeneity while minimizing interference with drift time determination.
3Productivity
If sample gas is introduced through conventional inlets, then sample material reaches the ionisation source, but radial velocity components cause sample gas to reach the outer wall and reduce ionisation efficiency
Solution Approach 1:
The gas inlet design uses asymmetric flow patterns that guide sample gas along a controlled path toward the ionisation source. By creating a unidirectional flow pattern with minimized radial velocity components, the asymmetric inlet configuration ensures sample gas reaches the ionisation zone efficiently without striking the chamber walls, maximizing both throughput and ionisation efficiency.
Solution Approach 2:
The gas flow is redirected from a radial pattern (which causes wall impingement) to an axial pattern that moves sample gas along the length of the reaction chamber toward the ionisation source. This dimensional change in flow direction eliminates the radial velocity problem while maintaining effective sample delivery to the ionisation region.
Data Source
AI summary
Ion mobility spectrometers and methods for determining an ion mobility spectrum of a sample are provided. The ion mobility spectrometers comprise a drift chamber and a cylindrical reaction chamber, wherein the drift chamber is designed to transport ions from a switching grid to an ion detector against an axial drift gas flow. The reaction chamber has a sample gas inlet adjacent to the switching grid for introducing a sample gas, a gas outlet opposite the switching grid for discharging drift gas and sample gas, and a local ionisation source arranged at the gas outlet. The sample gas inlet comprises gas inlets arranged oppositely on an inner circumference of the reaction chamber. The methods operate the ion mobility spectrometers to determine an ion mobility spectrum of a sample.