I am trying to determine the amount (for example mg or moles) of amino acid that can be loaded into a Dowex 50Wx4 column with a resin bed volume of 1.8ml. The resin has an exchange capacity of 1.1 meq/ml (milliequivalents per milliliter), but how do I use this information to calculate the (at least theoretical) number of moles or the mg of amino acid that can be captured?
Obviously all parameters (temp, flow rate etc) will affect this. However, based on a given meq/ml of a resin, it must be possible to calculate a theoretical value of how much of an analyte that resin can capture/bind. (I am doing “simple” chromatography with gravity fed mini columns and pH gradient elution).
The question in short: How do I calculate the amount (mass or moles) of an analyte that a specific amount of an ion exchange resin can capture?
Any input is greatly appreciated.
You need to calculate the equilibrium concentration of the amino acid in the ion exchanger with a total exchange capacity(TEC) of 1.1 meq/ml and a constant of exchange equilibrium K = 2.5 (we accept). Look for your resin.
1. Record the ion exchange reaction and the equation for the equilibrium constant
2. Indicate the desired amino acid concentration A + = x. Therefore, H + = TEC-x
3. Write down the equilibrium concentration of H +
4. Write down the equilibrium concentration of A +
5. Substitute the obtained concentrations in the quadratic equation of ion exchange
6. Solve the quadratic equation for x.
Dear Dr Mirgorod and Dr Wahab,
Thank you for your input, it is greatly appreciated.
Sincerely,
Nicolai
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