Membrane Interface for Mass Spectrometry
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Solution Overview
Problem
Existing membrane introduction mass spectrometry (MIMS) systems face issues with irreproducibility, long response times, high detection limits, and require extensive sample preparation, making them inefficient for analyzing low-level environmental contaminants.
Innovation Solution
A membrane probe design that integrates a capillary or sheet membrane with a needle to form part of a flow path, allowing for direct coupling to a mass spectrometer at atmospheric pressure, with a liquid or gaseous sample introduced on one side and a solvent on the other, enabling efficient ionization of volatile molecules through electrospray or other ionization methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional MIMS systems use membrane introduction with EI or CI sources, then volatile molecules can be ionized in the gas phase, but the systems suffer from irreproducibility, long response times, and high detection limits
Solution Approach 1:
The patent merges the membrane introduction interface with the electrospray ionization source, integrating the sample introduction and ionization functions into a single coupled system. This integration eliminates the separate transfer line and intermediate steps, reducing memory effects and improving reproducibility while maintaining low detection limits through direct coupling of the membrane to the ESI needle.
Solution Approach 2:
The patent changes the ionization parameter from electron ionization (EI) or chemical ionization (CI) to electrospray ionization (ESI), operating at atmospheric pressure instead of vacuum. This parameter change enables direct liquid introduction through the membrane without pervaporization, improving response time and reproducibility while maintaining sensitivity.
2Measurement precision
If purge-and-trap analysis is used to concentrate volatile compounds, then detection sensitivity improves, but the method requires bulky apparatus, sample carryover, contamination, and is expensive
Solution Approach 1:
The patent extracts the concentration function from the complex purge-and-trap apparatus and implements it directly at the membrane interface through electrospray ionization. The membrane itself serves as the concentration interface, eliminating the need for separate purge tanks, traps, and complex gas flow systems, thereby reducing device complexity while maintaining detection sensitivity.
Solution Approach 2:
The patent uses the membrane as an intermediary that directly introduces concentrated volatile molecules from the liquid phase to the ionization source. This membrane intermediary replaces the complex purge-and-trap apparatus, providing a simpler path for sample introduction while maintaining concentration capability through the membrane's selective permeation properties.
3Loss of time
If headspace analysis is used for volatile compound detection, then sample preparation time is minimized, but the method is limited to high concentration contaminants only
Solution Approach 1:
The patent performs preliminary concentration of volatile molecules at the membrane interface before ionization. The membrane selectively concentrates volatile compounds from the liquid phase, enabling detection of low concentration contaminants without requiring lengthy sample preparation or concentration steps, thus maintaining fast analysis while expanding the detectable concentration range.
4Measurement precision
If liquid-liquid extraction is used to analyze volatile organic compounds, then contamination is reduced, but large quantities of solvents are required making the method expensive and environmentally unfriendly
Solution Approach 1:
The patent replaces the mechanical liquid-liquid extraction system with a membrane-based selective permeation system coupled to electrospray ionization. This substitution eliminates the need for large volumes of extraction solvents, reducing waste and cost while maintaining contamination reduction through the membrane's selective separation properties.
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 design enhances the sensitivity and selectivity of MIMS, achieving low detection limits and rapid analysis of volatile organic compounds, with improved signal-to-noise ratios and reduced sample preparation time, suitable for real-time monitoring of contaminants in various matrices.
Implementation Method 1
small molecules are selectively concentrated by adsorption and separated from the water by preferential permeation through a membrane
Implementation Method 2
the volatile molecules that permeate the membrane go under a pervaporization process on the other side of the membrane where they are desorbed from the membrane surface and can then be ionized in the gas phase
Implementation Method 3
small molecules are selectively concentrated by adsorption and separated from the water by preferential permeation through a membrane
Data Source
AI summary
The disclosed method and apparatus couple a membrane interface directly to a mass spectrometer at atmospheric pressure. The membrane may be in capillary or sheet form and allows the introduction of a liquid or gaseous sample to one side of the membrane while the other side of the membrane is bathed with a solution that can easily be used in an atmospheric pressure ionization source. Volatile molecules permeate through a suitable membrane such as poly-dimethyl silicone (PDMS), mix into the appropriate solvent, and are ionized. Because of the rules governing abstracts, this abstract should not be used in construing the claims.