Membrane Inlet Mass Spectrometer with Selective Permeable Membrane
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Solution Overview
Problem
Existing Mass Spectrometry systems using Membrane Inlet Mass Spectrometry (MIMS) face limitations in detecting larger molecules such as pesticides and explosives due to slow diffusion through semi-permeable membranes, and struggle to differentiate between unsaturated and saturated hydrocarbons, requiring separate analyzers and facing sensitivity issues with high temperatures that can degrade analytes and contaminate electrodes.
Innovation Solution
Employing a selectively permeable membrane like Dow Corning™ Silastic™ Q7-4750, which allows unsaturated hydrocarbons like BTEX to pass through while blocking saturated hydrocarbons, and using a radiation source for non-contact heating of the membrane to enhance diffusion without sensitivity loss, along with multiple membrane configurations for targeted selectivity and improved detection of low concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If higher membrane temperatures are used to speed diffusion of larger molecules, then diffusion rate is improved, but sensitivity is reduced and electrode contamination increases
Solution Approach 1:
The patent changes the physical-chemical parameters of the membrane material itself rather than relying solely on temperature increases. By modifying membrane composition (cross-linked mixture of compounds with specific wt.% ranges) and physical state (softening point range), the membrane achieves enhanced permeability to larger molecules at lower temperatures, thus maintaining sensitivity while improving diffusion rates.
Solution Approach 2:
The patent employs a composite membrane material consisting of a cross-linked mixture of multiple compounds with specific properties (first compound: 0.0-75.0 wt.% Dimethyl siloxane, dimethylvinyl-terminated; second compound: 55.0-75.0 wt.% Dimethyl siloxane, dimethylvinyl-terminated). This composite structure provides both high permeability to larger molecules and stability at operating temperatures, resolving the contradiction between diffusion rate and sensitivity.
2Speed
If higher membrane temperatures are used to speed diffusion of larger molecules, then diffusion rate is improved, but electrode contamination increases
Solution Approach 1:
The patent changes the membrane's physical parameters (softening point range: -50°C to +50°C) and chemical composition to achieve optimal performance at lower operating temperatures. This prevents thermal degradation and volatilization of membrane materials that would otherwise contaminate electrodes, while still enabling adequate diffusion of larger molecules through the modified membrane structure.
Solution Approach 2:
The cross-linked composite membrane material provides thermal stability and structural integrity at lower operating temperatures, preventing decomposition and volatilization that cause electrode contamination. The specific composition ratio and cross-linking structure ensure both low-temperature operation and high permeability to target analytes.
3Adaptability or versatility
If separate analyzers are used for unsaturated and saturated hydrocarbons, then detection capability is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by creating membranes with specific localized properties (composition, softening point, cross-linking density) that provide selective permeability to different hydrocarbon types. Different membrane formulations can be used in different locations or configurations within a single analyzer to detect various hydrocarbon classes, eliminating the need for multiple separate analyzers.
Solution Approach 2:
The patent develops a universal membrane-based detection platform that can analyze both unsaturated and saturated hydrocarbons using a single mass spectrometer system. By varying membrane composition and properties, the same instrument can be adapted to detect different hydrocarbon types, providing multi-functionality without requiring separate specialized analyzers.
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
Enables the detection of low levels of unsaturated hydrocarbons in air and water with improved sensitivity and specificity, reducing interference from saturated hydrocarbons and maintaining analyte integrity, allowing for more robust and portable mass spectrometer designs.
Implementation Method 1
analyte molecules pass thorough the semi-permeable membrane by diffusion
Implementation Method 2
A semi-permeable membrane interface (e.g., a silicone polymer) separates a gaseous or liquid sample matrix from a much lower pressure region that is created within a mass spectrometer. Analytes, e.g., molecules, pass through the semi-permeable membrane preferentially
Implementation Method 3
using a radiation source for non-contact heating of the membrane to enhance diffusion
Data Source
AI summary
A system for analyzing an analyte is described herein. The system includes a chamber having an inlet and a semi-permeable membrane arranged to seal the inlet. The semi-permeable membrane includes a cross-linked mixture of a first compound and a second compound. The system can also include a radiation source arranged in the vacuum chamber, the radiation source spaced apart from the semi-permeable membrane and adapted to irradiate the semi-permeable membrane with electromagnetic radiation at a frequency at least partially absorbed by the semi-permeable membrane.