2016-11-18 at 1:52 AM UTC
The general starting point of any extraction is to liberate the target molecule from the material that houses is. For most extractions this is done in the initial acid phase. In this phase the material containing the target molecule is mixed with an acidic solution which liberates the target molecule from the housing molecule. The general rule is that you will get the target molecule in the form of acetate (salt). From this phase we move to the basic phase but before we go into that we will discuss the potential intermediary salting phase.
In some extractions it may be pertinent to salt the acetic solution just before the basic phase. This is just as it sounds, where you add salt to the extraction vessel/solution. The theory is that the salting helps push out more of your target molecule.
After this salting step (if it is implemented) the basic phase is commenced. In this phase the salt (not from the salting phase but the target molecule that is in salt form in the acidic solution) is converted to freebase by adding a very basic solution to a rather acidic solution.
After the target has been converted to freebase form the final process will take place. And this is where my use of the term "phase" was less than ideal. You see, for your basification of the acidic solution there was no separation of liquids into distinct phases. For this phase there will be distinct phases of liquid as one would see with water and oil. But perhaps I am getting ahead of myself. The general method is to use some sort of solvent (generally non polar) to pull the freebase form of the target molecule from the basic solution into the solvent.
Before we go further it would be pertinent to explain the entire process that just occurred. What we have done is 1. liberated the target molecule from the housing material. In this phase we have the salt of the target molecule, which is fine and dandy except for the fact that it will not be picked up by the solvent. 1.5 we use salt to further push the salt form of the target molecule from the acidic phase. 2. We convert the salt to freebase form which can be picked up by the solvent. 3. We add the solvent which picks up the freebase form of the target molecule. In fake math shorthand (we will use tm for the term target molecule AND will leave out the salting step) : Housing material + acid = salt of tm | salt of tm + base = freebase of tm | freebase tm + solvent = freebase tm + solvent.
So at this point we have the freebase target molecule inside the solvent. We have nearly reached the end of the general process. The only problem is that you dont have the target molecule by itself but rather a suspension of your target molecule in the solvent. Remove the solvent phase from the basic phase. Luckily most solvents used have a reasonably rapid evaporation rate. What this means is that you can evaporate your solvent and it will leave behind the target molecule. There are of course other options considering the solvent used. In some cases you can store the solvent at an extremely low temperature and the target molecule will precipitate out of the solvent. You can then decant the solvent from the precipitate and you will have your fairly pure target molecule. And of course there are other methods but these are the most common.
