How to flush a 10ml volumetric flask with liquid Nitrogen before preparing a sol - (Jun/24/2009 )

I need to flush a very small 10ml volumetric flask with nitrogen before I make up a folate standard solution in it. So I guess the purpose is to get the oxygen out of the flask so that my folate standard does not oxidize. I am not exactly sure what the best method is to do this procedure. I can see just holding the flask opening into the nitrogen gas attachment in the hood for a minute or so and then putting the glass stopper in. However, I still need to take the stopper off and add my powder and buffer solution up to 10mls and then oxygen will get back into the flask?? Does anyone know what the best way is to flush a volumetric flask with nitrogen gas??

Thanks

-libsdutch-

Best thing would be to constantly flush the flask with Nitrogen using a small hose. But if you are fast enough it should be okay to fill it with nitrogen once at the beginning.
Nitrogen is more dense than air, so it wouldn't get out of the flask too fast.

-mastermi-

You could also consider degassing the buffer and/or forcing nitrogen through it to reduce the O2 levels further.

-swanny-

libsdutch on Jun 24 2009, 09:28 PM said:

In this case I would:

1. Weigh the folate in the flask.

2. Put a glass pasteur pipette connected to a nitrogen source down the neck of the flask, and just into the "bowl".

3. Flush with a VERY gentle stream of nitrogen for 2-3 mins

4. Add 5-6 ml degassed buffer, gas the head-space of the flask again, replace stopper. Mix to dissolve.

5. Add degassed buffer to the final volume. Gas the head space again. Mix

You can make degassed buffer by passing a strong stream of nitrogen through the a flask of buffer for 3-5 mins.

Hope this helps

-klinmed-