Membrane to cover vial and allow alcohol vapor to pass

[dwalter68]

I am working outside my area of expertise and need help selecting a membrane to meet the following criteria:

-To be used as a septa for a small autosampler vial. The vial will be used as a test device for a chemical sensor.

-The vial will hold a liquid sample of 1-propanol or 1-octanol at room temperature.

-The membrane will keep the liquid alcohol inside the vial, but will allow a reasonably high permeation rate for the alcohol vapor. (Not sure what rate I need yet.)

-Must be easy to cut into small circles to fit the vials. Preferrably it would be somewhat soft and have some thickness so that it would provide a liquid tight seal between the screw cap and the vial.

Can anyone help?

 

[aspearin1]

Tough call... You will want something fairly non-wetting, but allowing vapor to escape. However, propanol is a very good wetting agent for membranes. Isopropanol is often used for this. 1-propanol may be a different story. I imagine 1-octanol would be different though. I would suggest using a highly hydrophibic membrane... a polyolefin such as polypropylene of polyethylene. You will probably need something below 0.1 micron pore size. I think what you will end up with is a spill resistant vial, but in the end you will have to rely on gravity to keep your vial from leaking, assuming your vial is not positioned upside down.

ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee