Lillica - 5-7-2017 at 16:20
I have some IRA 900 resin that I ordered from Sigma and have been trying to get some solid information about the anion molar capacity of the resin.
Sigma's product page lists "1.0 meq/mL by wetted bed volume". I'm not really sure what this meant, so I called their technical support asking for
clarification, and the guy that I spoke to didn't seem to know what he was talking about.
I have found a few sources including one patent suggesting that the IRA 900 resin has a molar capacity around 3-4.2 mmol/g. This particular patent was
in reference to the preparation of Borohydride resin, and they explained all their math, including the analysis of resin by percentage weight of boron
and by weight of hydrogen after treatment.
I've come across some other comments around the web saying that the the resins only have around 1mmol/g loading capacity. I just can't find a straight
answer on this topic and Sigma has been no help.
I'm sure a few people here have experience with these resins and have researched this topic before. I've exhaustively google searched before coming
here to ask this.
Dr.Bob - 5-7-2017 at 18:31
I would guess that they really mean 1.0 mmol per mL, but the numbers vary a lot. Also, as you use the capacity, some sites in the resin become
inaccessible, so I always assume that the loading is less than advertised, as that is how it works in real life. 3-4 seems a little high to me.
Melgar - 5-7-2017 at 20:55
It varies depending on the ion and the age and quality of the resin, and quite a bit too. The only way to know for sure is to test it experimentally.
Since you already have the resin, can't you just do that? Weigh the resin, then make a column from a length of tubing, and run a standardized
solution of your ion through it. When you start seeing that ion come through on the other end, stop, then calculate its loading.
Since the resin will change its loading capacity over its life, you should probably have a means of detecting when it's saturated, rather than expect
it to be able to hold a constant amount.