Permeation Tubes and Diffusion Tubes
The Vertical Owlstone Vapor Generator (V-OVG) is designed to be compatible with both permeation tubes and diffusion tubes. But what exactly are permeation and diffusion tubes? This at-a-glance guide will help to make that clear.
Permeation Tubes
A permeation tube is a sealed cylinder of a permeable material (such as PTFE) with an analyte of interest inside. The analyte will very slowly permeate through the walls of the tube, at a rate governed by temperature and tube geometry.
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| Permeation tube schematic | Permeation tube |
Diffusion Tubes
A diffusion tube is a container with an opening at the top (which may be covered with a permeable membrane). Gas evaporates from a reservoir of sample at the bottom of the tube, and diffuses upwards at a rate governed by temperature, pressure and tube geometry.
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| Diffusion tube schematic | Diffusion tube |
Performance Comparison
| Permeation Tubes | Diffusion Tubes |
| Come ready-made to load into OVG-4 and V-OVG | Can be used with the V-OVG |
| Some compounds cannot be made into permeation tubes | Any substance with a sufficiently high vapor pressure can be used |
| Can produce very low concentrations (ppm to ppb) | Can produce higher concentrations |