Wednesday, January 07, 2009

Whatman Phase Separators

I hope everyone had a merry Christmas and I wish you all a happy and prosperous New Year. Time for the first post of 2009.
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A former colleague of mine introduced me to the ingenious invention: Phase Separators. This is a big help in the lab and really saves me a lot of time, particularly with qualitative work. A Phase Separator is essentially a piece of filter paper that has been treated with silicone. If you fold it up and stick it in a funnel and pour a mix of organic solvent and water on it it will only let the organic solvent pour through. It only works well with solvents more dense than water, typically dichloromethane or chloroform. They are best employed for qualitative work where all that's required is a quick NMR to determine a ratio between isomers, whether a reaction is finished etc. For this type of work I basically transfer my reaction to a separation funnel with dichloromethane and wash it with appropriate aqueous phases. After the final wash the whole thing is poured directly into a Phase Separator, the organic phase is collected in a round bottom flask and concentrated in vacuo. I never observe any residual water in my NMR spectra so drying the organic solvent is unnecessary. D!

19 comments:

Tim said...

What kind of volumes can you put through it?

Daniel Sejer said...

The largest filter papers I have (15 cm diameter) can retain about 40 ml aqueous phase (the way I fold them). You can however get diameters up to 27 cm or even sheets measuring 28 x 46 cm. There is more info on this web site: http://www.whatman.com/1PSPhaseSeparators.aspx. D!

Anonymous said...

what is the advantage over the sep funnel? Particularly when the density of the solvent is heavier than water??

Daniel Sejer said...

You don't have to wait for the phases to separate and, more importantly, you don't have to dry your organic phase to remove residual water. D!

Anonymous said...

Oh D! you always were a lazy bastard!

Lysén

Daniel Sejer said...

Hey Lysen, surely you mean efficient and technologically up to date, right? D!

Anonymous said...

It seems to be nice thing for fast separation of phases - thanks a lot!
But concerning drying - residual water goes as an aseotrope with DCM or CHCl3, the same as with toluene. One guy taught me no to dry an organic phase if it contains a lot of DCM, toluene or CHCl3. After separation of pases we just pass it throug a plug of cotton to get rid of droplets and go to a rotavap directly.

Daniel, one question: If you have a nasty emulsion, does it speed up separation? Thanks.

ChcltBrcn said...

Quote: "One guy taught me no to dry an organic phase if it contains a lot of DCM, toluene or CHCl3."

Why is this?

Daniel Sejer said...

Firstly, I've tried filtering emulsions on 1PS filter paper and unfortunately it doesn't work (hardly surprising really). Secondly, I'm sligtly confused about the azetrope story. I'll have to look this up when I get to work next week. I thinhk most of us know about the toluene/water azetrope, but I'm not familiar with the CHCl3, CH2Cl2/water azeotropes. I'll get back to this. D!

Daniel Sejer said...

I should mention one more thing. When you filter on 1PS filter paper the separation is instantaneous. There is no waiting around to get the last couple of drops through the filter paper. The organic phase essentially falls through. Much more convenient than cotton, glass wool or standard filter paper and it's cheap too. Whatman should pay me for this free advertising. D!

CARBON CHEMISTRY said...

oh.. its excellent. Thanks for this. I enjoy reading your blog very much..

James said...

Biotage also make similar things aimed more at small scale parallel synthesis.
http://www.biotage.com/DynPage.aspx?id=25351

ChcltBrcn said...

Perhaps a little Off-topic but, does anyone know about the Waters FractionLynx purification system? I have a guy running one in my department and both times I've used it it's given incredible results, separating stereoisomers and really nasty halogenated mixtures. I don't have a clue how it works though...

almostthere said...

totaly interested. im working on 500 -140 ug scale and havent been able to get the water out of my NMR spectra. Anybody use this paper on that small of a scale?

Anonymous said...

To ChcltBrcn: there is no big sense in drying if water will be removed anyway via an azeotrope. Let say if you do not want to mess with MgSO4 you can extract your water phase with EtOAc, add to your combined organic phase some toluene or CHCl3 or DCM (ca 1/4), wash this new combined organic phase with brine, filter through a small plug of cotton and concentrate on vacuum. No water should be left.

peach said...

I found fabric spray (sprayable silicone) can turn a piece of ordinary filter paper into a MAGIC filter paper. 8P

And I made a video...

http://www.youtube.com/watch?v=GzlnaKW1wcQ

peach said...

If you're interested in separation, and these papers, you might like the discussion going on at;

http://www.sciencemadness.org/talk/viewthread.php?tid=14613#pid189554

I know some of you are actual, real life, well funded lab chemists, and probably have access to equipment that can test for the better hidden effects.

Anonymous said...

"It only works well with solvents more dense than water" I forwarded caution to lab using filter for hexane/water separation for quant work. The lab contacted Whatman and claims density should not matter. Any thoughts?

Daniel Sejer said...

@Anon.: I guess it is a matter of opinion if it works well or not with solvents lighter than water. Try it and see what you think. If you only have a very small amount of water it works OK with the lighter solvents although it takes a while. However, if you have a larger volume it takes a long time for the separation to take place because most of the filter is occupied by the aqueous phase. D!