Nitrogen use for evaporation

[mtorrey]

Hello

It looks like I will have to use nitrogen to dry down my samples for this phospholipid procedure I'm developing (we currently use pumped air).

My question is for those of you who use nitrogen for drying down solvent extracts; how much nitrogen do you go through in a typical day? We will be doing about 10 to 25, 1 mL specimens a day using a Pierce evaporator (2 PSI). We are thinking of using "G" cylinders.

TIA

Mike

[Keaka]

The amount of nitrogen you'll go through will depend on what solvent your extracts are in.. some will evidently evaporate faster than others which will affect how long your nitrogen is flowing.

Are you doing 10-25 at the same time? or sequentially?

[mtorrey]

Some extractions are in a Methylene Chloride/Ethylene Chloride/Heptane mixture, these dry down in 10 minutes.

The phosphatidylglycerol I'm working on is in chloroform and take about 20 minutes to dry down.

Specimens are extracted as demand dictates. There is no batching.

In a recovery experiment I dryed down 6 samples from a single "line" one at a time from the nitrogen tank we use for a GCFID and the pressure dropped 100 psi. So I'm thinking if we do switch to nitrogen to dry down all of our samples we're going to be using a lot of it. Maybe more than it's worth.

If I knew what the flow is at 2 psi I could figure it out but I don't know that.

Mike

[HW Mueller]

There are all kinds of flow meters, but what for? You already know how much gas you use. One can optimize the evaporation by moving the nozzle close to the surface of the liquid, denting the surface of the solution slightly, one should never cause bubble formation as one looses nonvolatiles via aerosol formation. Also heating during evaporaton helps.
Rotary evaporation is often an alternative.