Re: Need a recommendation on a good vacuum pump for removal of high boiling solvents

Eli.Zukowski@xxxxxxxxx wrote:
>
> Hey Everyone
> This is my first post here but I've been a lurker for a bit. Anyways
> the lab I'm working in has got a few old Welch Duoseals(couple 1399's
> and a 1400) but unfortunately they've seen so much general use that
> they don't pull as good a vacuum as they should. Now we're looking at
> getting a new high vac specifically for removal of small amounts
> (probably under 20mL's) of high boiling solvents, specifically DMSO and
> DMF.
>
> I've looked around and done some reading and right now I think the
> choice is between getting another Welch Duoseal, an Alcatel, or an
> Edwards. We really want to get something that will pull and maintain a
> nice low vacuum to a couple millitorr, and will be rugged and
> dependable with good normal maintenance. I'd really appreciate it if
> people could toss me some suggestions or any good or bad experiences
> with any pumps they've used. Thanks a lot!

A direct drive pump with direct drive oil protected with an
intermediate cryotrap - at least Dry Ice/acetone and preferably liquid
nitrogen. Durp the solvent pot to local cryotrap, not into the pump
trap. For 20 mls you could diddle a dewar condenser directly into the
pot. DMF is not bad but DMSO is a bitch. Make all the bores
including stopcocks as large as you can, and all the runs as short as
you can.

Almost any roughing pump can get down to 5 microns hooked to a
pressure gauge. The trick is pumping down a real world volume with
stuff happening in it. If you have the budget, think first.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
.

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