Chromatography Forum

Hello,
I am trying to use a flow of nitrogen to isolate EPS (exopolymeric substance) mostly composed of carbohydrates and proteins from ethanol/H20 solution.

I do not know how to set up a flow of nitrogen, It is about max 100 mls (20 % H20 and 80% ethanol).every couple of weeks. Could I set up some sort of wand that emits N2 gas which I can aim at my solution.

Comments, Questions, Suggestion, diagrams, solutions and paper suggestions for reading material are all recommended. Thanks.
Vanessa

A common solution in the laboratory for handling a few samples at a time, each being on the order of milliliters or less, is to slide the large end of a Pasteur pipette into laboratory tubing and attach the laboratory tubing to a nitrogen bottle or line. Using the outlet valve on the nitrogen supply, you can adjust the flow that you have a gentle stream of nitrogen coming through the pipette. The pipette can be held with a ring stand clamp to hold it in a fixed position.

For a sample of about 100 mL, I would aim the flow of nitrogen at an angle down the side (inside) of the container causing the surface of the liquid to dimple slightly and the gas flow to cause the solution to turn. The trick is a slight dimple -- do not splash.

Thank you so much for your time and responding to me, it is much appreciated.

-A struggling grad student

Evaporating 100 ml of 80% ethanol with a stream of nitrogen will take hours. You would be better with a rotary evaporator to evaporate the bulk of the solution, and then use nitrogen when the volume has been reduced to a few ml.

Peter

Agreed with Peter, entirely! Gentle warming also helps the process (obviously drying solvent cools the sample; the energy for evaporation has to come from somewhere). If you can find a hot-block of some sort which fits your sample vessel(s), it will help (don't over-heat if your sample is labile).

For drying large numbers of samples of smallish volume, I once made a manifold consisting of a lunch-box attached to a nitrogen line, with loads of hypodermic needles stuck through at the correct spacing to match a dry-block heater we had in the lab. It was lethal (think compressed-air-driven explosive porcupine) but it did the job. Commercially you can get waterbaths with a nitrogen manifold fixed above them for this purpose.

When you're no longer a stressed grad student but a happy Professor, there's another bit of kit you might like to buy: it is possible to get shakers that have a hot-block that is orbitally shaken, and maintained under vacuum. The way these work is exactly the same as a rotary evaporator, but they can handle 20 samples at once.

When you're no longer a stressed grad student but a happy Professor, there's another bit of kit you might like to buy: it is possible to get shakers that have a hot-block that is orbitally shaken, and maintained under vacuum. The way these work is exactly the same as a rotary evaporator, but they can handle 20 samples at once.

Imh, i am curious, could you give me a link to the kit explained above?

Thanks

The thing we have is an obsolete Buchler vortex evaporator salvaged by a coworker. I believe the modern-day equivalent would be something like:
http://www.buchi.com/Parallel-Evaporati ... tm_id=paev

The thing we have is an obsolete Buchler vortex evaporator salvaged by a coworker. I believe the modern-day equivalent would be something like:
http://www.buchi.com/Parallel-Evaporati ... tm_id=paev

Thank you!