I am activating Dowex 50 resin for column chromatography. I need to know whether after following the activation protocol, it is activated or not. Can anyone help me?
8/14/15
Dear Somya,
A little more information would be helpful to answer your question. Dowex 50 is a strong cation exchanger, and can be in several forms. Depending on how you plan to use it, it can be in the protonated or hydrogen form (-SO3-H), or the salt form with the hydrogen replaced by a cation such as sodium or ammonium, e.g.,, i.e., -SO3NH4), etc. .How did you activate the resin? If you washed the resin with acid to put it in the hydrogen form, then wash the resin with deionized (DI) water to remove the acid until the pH is that of DI water. Then, take a small amount (~0.1-0.2 mL) of resin in a test tube and add some NaCl (~0.10 - 0.2 M). If the resin was properly activated and is in the hydrogen form, addition of NaCl will displace some of the H+ from the resin and the pH of the water will become acidic. This you can check w/ pH paper. If you put the resin in the -NH4 form, as above, put ~0.1-0.2 mL washed resin in a few ml of DI-water and add ~ 1 mL 1 M NaOH. This releases the -NH4 from the resin. Reaction with -OH will convert -NH4 to NH3. Heat the tube over a burner with a piece of moist pH paper over the tube mouth. The NH3 will give an alkaline reaction with the pH paper. You can also test for NH4 directly w/ test strips, e.g., QUANTOFIX® Ammonium test strips, which are commercially available.
I hope this helps you. If you need more information, let me know.
Bill Colonna, Iowa State University, Ames, IA USA [email protected]
If I will use Dowex 50 as H+ form, I will use 20-hold of column size of 1mol/L HCl solution. If I will use Dowex 50 as NH4+ form, I will use 100-hold pf column size of 1 mol/L CH3COONH3 solution. Of cource, I will wash the column with 10-hold of column size of distilled water after using above solution.
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