Hi Marcos,

There are several tricks to break emulsions which can be tried here. In my order of preference:

1. Freezing/thawing a sample, since the water solidifies first this may break your emulsion. Be sure to freeze it fast and put it in a refrigerator to let it gently thaw (although in some cases rapid thawing may also work).

2. Addition of salts, AlCl3 for instance. AlCl3 dissolves badly in toluene but it compresses the electrostatic double layer so that your emulsion may break.

3. Addition of an anionic surfactant for instance SLS (sodium laurylsulfate), this will cause precipitation of CTAB-SDS complex, however this complex is probably soluble in toluene and thus pollutes your organic phase.

4. Ultrasonication may sometimes work, but in most cases it may also enhance emulsion stability.

I would set out to try this on small aliquots and see which method works best in your case.

Kind regards, Leo

I'd add to the excellent and thorough answer by Leo above. I'd be looking at salting out first - say with NaCl analogous to item 2 above. I'd also ask for the reasons for the need for separation. If you need the organic phase, why not use an ether solvent extraction which will remove all the organic and leave the aqueous material behind?

Dear Leo .

Have you tried to evaporate toluene under normal conditions or by lowering the pressure with a vacuum pump? This could result.

Dear Pablo,

it was Marcos that had the question on this. Alas, Marcos needs the toluene phase itself, so evaporating it may cause loss of the substances it may contain. Evaporation in this case is not simple and may require an elaborate distillation setup.

But your remark is valid and appreciated for most other systems were one needs the aqueous phase!

Kind regards, Leo

Another alternative would be to alter the curvature of the surfactant brush by the addition of a surfactant that favors w/o emulsions, such as Aerosol OT.