Acid Base Extraction is a way of extracting organic compounds (often alkaloids; or nitrogenous bases) from a solution, or from plant matter. Many references on extracting drugs from plants are actually Acid Base Extraction procedures.

The procedure, while it may vary slightly depending on the desired result, is pretty much the same in all instances. This description is assuming that we are starting with an alkaloid that we want in a polar solution (water).

First a strong base, often NaOH is added to turn the molecule into a freebase. The freebase then percipitates out of solution, as it will no longer dissolve in the polar solvent (water).

A layer of non-polar solvent (like petroleum ether, or chloroform) is then added, and the desired freebase dissolved in it. The layers can then be run through a sepratory funnel.

If freebase is desired, then the solvent can just be evaporated off. Otherwise, more polar solvent can be added, and an acid (like HCl) is added to turn the freebase back into a salt and bring it into the solution.

As you can see, this works by changing the soluability of the chemical in question. This can be used to extract alkaloids from solutions where other chemicals are present. It can't however, extract one alkaloid from another.

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