Ionizer for Vapor Analysis Decoupling Ionization from Analyzer
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Solution Overview
Problem
Existing methods for ionizing vapors in gases at small concentrations face challenges such as dilution by counterflow gas, low ionization efficiency, and contamination issues, particularly when sample volumes are limited, leading to inadequate sensitivity and inefficiency in detecting trace species like explosives or volatile organic compounds.
Innovation Solution
The solution involves isolating the ionization volume from the counterflow region by using separate ionization and impaction chambers, with a small exit orifice to minimize counterflow dilution and employing a strong electric field to extract target ions efficiently, allowing for reduced sample flow rates and increased ionization probability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single chamber is used for both ionization and counterflow, then device complexity is reduced, but ionization efficiency deteriorates due to dilution by counterflow gas
Solution Approach 1:
The device is divided into two separate chambers: an ionization chamber where vapor ionization occurs, and an impaction chamber where the ionized vapor is introduced into the analyzer. This segmentation prevents dilution of ionized vapor by counterflow gas, thereby maintaining high ionization efficiency while managing device complexity through functional separation.
Solution Approach 2:
The counterflow gas is extracted and isolated from the ionization chamber by introducing it separately into the impaction chamber. This extraction ensures that the ionization chamber maintains its high concentration of ionized vapor without dilution, while the counterflow gas performs its function of introducing sample into the analyzer.
2Quantity of substance
If sample flow rate is increased to improve detection sensitivity, then more vapor molecules are available for ionization, but dilution by counterflow gas increases reducing ion concentration
Solution Approach 1:
By separating the ionization and impaction functions into different chambers, the system can handle larger sample flow rates in the ionization chamber without suffering from counterflow dilution. The segmented design ensures that ionized vapor concentration is maintained while allowing increased vapor sample amount to be processed.
3Productivity
If exit orifice size is increased to improve ion transmission, then more ions can reach the analyzer, but counterflow gas penetration into the ionization chamber increases causing dilution
Solution Approach 1:
The separation of ionization and impaction chambers allows the exit orifice to be optimized for ion transmission without compromising ionization efficiency. The segmented design prevents counterflow gas from penetrating into the ionization chamber through the orifice, as the orifice is positioned in the impaction chamber rather than the ionization chamber.
Solution Approach 2:
The impaction chamber acts as an intermediary between the ionization chamber and the analyzer. It receives ionized vapor through the exit orifice and introduces it into the analyzer while preventing counterflow gas from entering the ionization chamber, thus protecting the ionization efficiency.
4Productivity
If electric field strength is increased to improve ion extraction, then ionization efficiency improves, but energy consumption increases
Solution Approach 1:
The segmentation of ionization and impaction chambers allows the electric field to be applied more efficiently in the impaction chamber for ion extraction and introduction into the analyzer. This reduces the overall energy requirement compared to applying a strong electric field throughout a single large chamber.
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 significantly enhances the sensitivity and efficiency of vapor ionization, allowing for higher conversion of vapor molecules into ions and improved detection limits, even with limited sample volumes, by minimizing dilution and contamination, and enabling the analysis of trace species at lower concentrations.
Implementation Method 1
Vapor species are ionized by contact with an electrospray cloud
Implementation Method 2
A flux of target ions sufficiently strong to fill most fluid streamlines sampled into the analyzer is drawn from the ionization chamber (primarily by the electric field)
Implementation Method 3
A jet of sample flow leaves the ionization chamber through said exit orifice, and impacts frontally against the counterflow jet originating from the bottom of the impaction chamber
Data Source
AI summary
A method and apparatus are described to increase the efficiency with which a sample vapor is ionized prior to being introduced into an analyzer. Excellent contact between the vapor and the charging agent is achieved in the ionization chamber by separating it from the analyzer by means of a perforated impaction plate. As a result, some desired fraction of the gas going into the analyzer or coming out of the analyzer can be controlled independently from the flow of sample through the ionization chamber. Furthermore, penetration into said ionization chamber of said desired fraction of the gas going into or out of the analyzer is minimized by controlling the dimensions of said perforated impaction plate. Ions formed in the ionization chamber are driven partly by electric fields through said hole in said perforated impaction plate into the inlet to the analyzer. As a result, most of the gas sampled into the analyzer carries ionized vapors, even when the sample flow of vapor is very small, and even when the analyzer uses counterflow gas.