[IsotopeBill]

Synthetic chemists often have to purify commercially-available reagents, and the methods are often well-defined,a nd the criteria are well-defined as well.  But what about something like "starch"?  This has a fair amount of variability, right?  How might it be purified? and how to define it?

Thanks for any ideas.

[Babcock_Hall]

I have not done a literature search, but one possibility would be to fractionate it by size on a gel filtration column.  It could also be treated with ion exchange resins to remove unwanted ions.

[Arkcon]

You will have to define it, before you can purify it.    At least, you will have to define your application, and identify what impurities, at what level, you need removed, before the starch is adequate for your application.

[mavybenson]

Is this a long process?

[furanosa2000]

Yes, strach do has a large variability. depends on its source, the growth condition of the source etc. the starch can have different molecular mass. And the difference between one molecule to another can be only one glucose molecule.. and that, in my opinion, would be very hard to be separated by gel filtration, except you can find a matrix that can separate molecules with about 100 Da differences. And to use gel filtration, you have to solubilize the sample. In case of starch, it doesn't  solubilize in cold water, but, in hot water it will form gel!! again that would be another problem for the separation. And one more thing to note, that the starch is not simply an individual compound, but mixture of amylose and amylopectin that forms granules.

As far as I know, the purification of starch is performed in a simple way. use water or ethanol to separate the starch from the other component from its source, and leave it until the starch precipitate. However, it is very hard to separate one molecule of the other. Just try to find a starch from a chemical company, and usually they will not give you the molecular mass of the starch molecules.

CMIIW