Bio-Rad Chelex® 100 Resin - Manual (Page 6)

capacity of the sodium form of the resin is 0.4 meq/ml
(defined as Cu(NH
3
)
4
+2 uptake).
Elution, Regeneration, and Conversion
Metals can be removed with Chelex chelating
resin using either the batch or the column technique,
though the column technique is generally more effi-
cient. The most effective agents to elute the metals
from the resin are acids. Concentrated salt solutions
are often useful for selective elution, but are generally
inefficient in removing strongly absorbed metals.
Regeneration of the resin to a salt form is a two-
step process. The resin is first converted to the hydro-
gen form using acid, then converted to the desired
ionic form using the hydroxide of the cation desired.
The regeneration to the sodium form of resin loaded
with copper would proceed as follows:
Resin-Cu + 2 HCl Resin-H + CuCl
2
Resin-H + NaOH Resin-Na + H
2
O
The following sequence should be used: 2 bed
volumes in 1 N HCl, 5 bed volumes water rinse, 2 bed
9
4. Slowly add the sample to the column, taking care
not to disturb the resin bed.
5. Initiate flow. Discard initial buffer from the void
volume.
6. If a metal free solution is the goal, collect effluent.
If the concentrated metals are of interest, allow all
of the sample to pass through the column, then
elute the metals off the resin with a solution con-
taining a counterion of higher selectivity than the
bound metal.
Ion Exchange
The quantity of cations exchanged is a function of
pH. Exchange is very low below pH 2, increases
sharply from pH 2 to 4, and reaches a maximum above
pH 4. Any metal removed from solution is replaced by
an equivalent amount of the ions originally on the
resin. Usually an alkali metal form is best. The resin is
supplied in the sodium form, but may be used in the
potassium or ammonium form as well. These weakly
held ions allow other ions to be readily adsorbed. The
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LIT200B 6/17/98 11:49 AM Page 8