Expert: Dr.Paul Skett - 5/24/2008

Question
sir,
 when we do liquid liquid extraction what is effect of adding 10%acid or any base and how do we know which has to be added and up to which concentration or microliter level we can add such buffers?
If any gel formation occurs at the time of extraction how it will affect the analysis? shall we continue the extraction with the same or have to drop that method?
thank u

Answer
Hi, Simi,

I assume you are using extraction to/from an organic solvent from a water-based one.

The idea of adding acid/base is to change the lipid (and therefore organic solvent) solubility of the components you want to extract.

For example, a fatty acid is more soluble in water as a salt (and, thus, in basic conditions) whereas it is largely insoluble in water in its uncharged state (in  acid conditions). So adding acid to the solution of fatty acid salt in water will render it water-insoluble and, thus, move it from the water to the organic solvent.

This is a standard extraction technique for organic acids and bases. Exact concentrations of acid/base need to be calibrated for each extraction.

Gel formation is difficult to deal with as you cannot be sure of the extraction (difficult to mix and separate). I would suggest changing the method unless you can show a decent extraction or the description of the method says to expect a gel formation.

Hope this helps.

Paul