Acidify the saponification step with an acidic resin (e.g. Dowex, Amberlite), filter, concentrate. This gives you a salt-free crude, it may be pure enough depending on what you plan to do with it.
I have never use acidic resin, would you please explain the procedure or kindly let me know the reference if you have.
thanks for your help.
Just think of it as a solid acid. You just add it to your reaction. The resin capacity can be found on the suppliers website, usually expressed in meq/g - this is milliequivalents per gram, for a monoprotic acid this is the same as mmol/g, and is usually in the 1-2 range. I would use an excess vs the KOH to make sure you get all the potassium out of solution.
As stated above, try to avoid using a huge excess of KOH if you're working on multigram scale or higher, otherwise you will need a lot of resin (but it can be regenerated, so this is not a massive problem). After adding the resin, stir the solution gently or you risk breaking the beads and creating fines that can block filter frits. Another option that avoids this potential problem is to pour your crude onto a column of resin and allow it to slowly drip through under gravity (resin contact time of 1 h should be plenty) and rinse off the resin with 2-4 bed volumes of MeOH. I favour this method, especially on larger scale, because it doesn't risk damaging the resin, which is important if you plan to regenerate and reuse it several times.