Degas

[harry2008]

Hi there,

The bubble formed in my process brought me a lot of trouble. I am wondering how I can degas the solution. My receptor solution is just DI water. I need to degas 1000 ml water completely for repeated application. I've used vacuum and stirring with a stir bar at the same time. I was also suggested to use Helium for degassing. I never used Helium. Could anyone tell me how I can play with He? How long should I degas 1000 ml water with Helium? What pressure? And why Helium works ? It sounds to me Helium is also a gas like Hydrogen so it should cause more bubbles. Why can He be used for degassing?

Many thanks!
harry

[tom jupille]

The problem with vacuum degassing is that it is a "one shot" technique. Once you remove the vacuum, your water begins to reequilibrate with air. It sounds like you need a continuous degassing process, so He sparging should work.

What you need to do is to connect a filter frit (the same kind you would use on the inlet of the HPLC) to your helium line and put it in the reservoir. Turn the He flow on so that you get good "rolling" bubbles (it should look about like vigorously boiling water) for a couple of minutes (it doesn't take long). Then turn the helium flow down until you can just barely see a fine plume of bubbles rising from the frit. That will keep a He "blanket" over the liquid and prevent contact with air.

He sparge works because He has a very low solubility. Dissolved N2 and O2 from your solvent diffuse into the He bubbles and are removed from the system, but very little He diffuses back into the solvent because of the low solubility.

[harry2008]

Thank you very much, Tom! I know you . It seems to be a simple process, but if it works, it may solve our big problem. I already did yesterday and waiting for my result. Best wishes! harry