A Question about Chromatography

[kalladin]

I calculated the total exchange capacity of a column per gram of dry weight of resin to be 2.74 meq/g. This value comes from experimental values. However, the manufacturer's specifications for the number of exchange sites is 3.4 meq/g.

1. What's meq? I know this means milliequivalents of the anion/cation, but what does it mean? I think I'm contradicting myself by asking the question, but please help out to clarify if you can.

2. Why would there be such a big difference between the experimentally determined number of exchange sites and the manufacturer's specifications? I suspect that when the resin is packed in a column some surface area is compromised?

Please help me out here

Thanks,

K.

 

[DocToxyn]

I'm not all that familiar with ion exchange chromatography, but I did some work with HPLC and GC and I think I can help. Classically, Meq provides the concentration of a substance, that is in ionic form, in solution, or more likely in this case the amount of ion bound to resin. Solutions of non-ionic sunstances should not be expressed in this manner. Thus if a solution contains 20 ppm of magnesium then the meq would be 1.67 (20/24 gives moles of solute, multiply by 2 for valence= 1.67). In many cases where the valence is one, the Meq equals a molarity based concentration. Does this answer your question?

To get to your difference between your's and the manufacturer's value, since this is an experimentally derived number, how many times did you do the experiment? Perhaps there is a considerable variation and with a larger number of replicates you would approach the reported number.

If this hasn't helped perhaps the Chemistry board would provide better results.

 

[Moonbear]

I agree, this would probably get a better answer on the Chemistry board. Hopefully one of the mentors will kindly oblige us and move the thread.