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.
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.
|Permeation tube schematic||Permeation tube|
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.
|Diffusion tube schematic||Diffusion tube|
|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|