Bio-Rad Bio-Rex® 70 Cation Exchange Resins - Manual (Page 4)

Table 1. Properties of Bio-Rex 70 Resin
Wet density 0.6 ml/g (Na + and H + forms)
% moisture 65-74% (Na + form); 55-65%
(H+ form)
Swelling 1 ml (H + form); 1.7 ml (Na+ form)
Capacity 10 meq/dry g
Na+ form 0.5 meq/ml
H+ form 2.4 meq/ml
Pore volume 0.10 cc/cc
Pore size range 700-4,000 Å
Thermal stability Up to 100 °C
Normal operating
pH range
5 to 14
Order of selectivity
for monovalent ions
H>>Ag>K>Na>Li
Order of selectivity
for divalent ions
H>>Fe>Ba>Sr>Ca>Mg
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sample ions that have the same charge. On a cation
exchange resin such as Bio-Rex 70 resin, neutral
molecules and anions do not interact with the resin.
Normally Bio-Rex 70 resin is supplied in the sodium
form, but the resin can be converted from one ionic form
to another. Usually the resin is used in an ionic form with
a lower selectivity for the functional group than the
sample ions to be exchanged. The sample ions are then
exchanged when introduced, and can be eluted by
introducing an ion with higher affinity for the resin or a
high concentration of an ion with equivalent or lower
affinity. Table 1 shows the relative selectivity of various
monovalent and divalent counterions, as well as some
nominal properties of the Bio-Rex 70 resin.
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