Passive Diffusion Sampler with Regenerated Cellulose Membrane
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Solution Overview
Problem
Conventional passive diffusion samplers face issues such as limited penetration of certain VOCs, fragility leading to sample bag tears, and air contamination during sample collection, which restrict their ability to capture a broad spectrum of groundwater contaminants effectively.
Innovation Solution
The use of a regenerated cellulose diffusion bag within a rigid, perforated PVC housing that protects against tears and allows for air-free sample withdrawal via a septa or flow control valve, enabling broader contaminant capture and preventing air contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyethylene bags are used for passive diffusion sampling, then the sampler structure is simple and easy to manufacture, but certain VOCs including ketones, ethers, and alcohols cannot penetrate the membrane effectively
Solution Approach 1:
The patent combines polyethylene and regenerated cellulose materials in a single bag structure. The polyethylene provides structural integrity and ease of manufacture, while the regenerated cellulose portion allows penetration of a broader spectrum of contaminants including ketones, ethers, and alcohols that cannot penetrate polyethylene alone.
2Ease of manufacture
If polyethylene sample bags are used, then the manufacturing process is simple, but the bags are inherently fragile and susceptible to tearing during deployment or retrieval
Solution Approach 1:
The composite structure combines polyethylene (providing toughness and tear resistance) with regenerated cellulose (providing contaminant permeability). This creates a bag that is both durable against snagging and tearing during deployment/retrieval and effective at capturing a broad spectrum of contaminants.
3Ease of operation
If samples are collected by removing bag cap and pouring into vials, then the sampling process is simple and quick, but the sample is exposed to ambient air causing contamination
Solution Approach 1:
The invention extracts the sampling function from the bag opening process. Instead of removing the cap and pouring samples (which exposes them to air), a piercable septa is installed in the bag cap, allowing direct extraction of samples through the sealed cap using a syringe or sampling device, thus eliminating air exposure while maintaining operational simplicity.
4Reliability
If a netting is added over the sampler to protect the bag, then snagging and tearing are reduced, but the device complexity increases
Solution Approach 1:
Instead of adding external protective netting (which increases complexity), the protection function is integrated into the bag material itself through the composite polyethylene-regenerated cellulose construction. The polyethylene component provides inherent toughness and tear resistance, eliminating the need for separate protective netting while maintaining reliability.
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 allows for the capture of a wider range of VOCs and other water contaminants while ensuring sample integrity by preventing tears and air exposure, providing a robust and contamination-free sampling system.
Implementation Method 1
passive diffusion samplers work by submersing a tubular low density polyethylene bag filled with analyte-free water into a ground water sampling bore hole. The polyethylene bag serves as a semi-permeable membrane that allows certain VOCs to diffuse through the membrane.
Implementation Method 2
Over time, an equilibrium is established between the VOCs in the bag and those in the groundwater.
Data Source
AI summary
A passive diffusion sampler and kit that includes a passive diffusion sample bag comprising a regenerated cellulose membrane to allow for sampling of a broad spectrum of contaminants and VOCs. The sample bag is disposed in a rigid housing which protects the bag from tearing and also allows the housing to be inverted to suspend the bag upside down and provide a user access to a fluid outlet means on the bag for withdrawing a sample from the bag without agitating the sample.