Bio-Rad AG® MP-1M Anion Exchange Resins - Manual (Page 6)

Table 3. Relative Selectivity of Various Counterions
Relative Selectivity Relative Selectivity
Counterion for AG 1 and for AG 2 Resin
AG MP-1 Resins
OH - 1.0 1.0
Benzene sulfonate 500 75
Salicylate 450 65
Citrate 220 23
I - 175 17
Phenate 110 27
HSO
4
- 85 15
ClO
3
- 74 12
NO
3
- 65 8
Br - 50 6
CN - 28 3
HSO
3
- 27 3
BrO
3
- 27 3
NO
2
- 24 3
Cl - 22 2.3
HCO
3
- 6.0 1.2
IO
3
- 5.5 0.5
HPO
4
- 5.0 0.5
Formate 4.6 0.5
Acetate 3.2 0.5
Propionate 2.6 0.3
F - 1.6 0.3
7
AG MP-1, neutral species and cations do not interact
with the resin. In the chloride form of AG 1, AG MP-1,
and AG 2 resin, the counterion on the resin is Cl
- . A
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
onto the resin 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 3 shows the relative selectivity of various
counterions. In general, the lower the selectivity of the
counterion, the more readily it exchanges for another ion
of like charge. The order of selectivity can also be used
to estimate the effectiveness for different ions as eluants,
with the most highly selective being the most efficient.
Finally, the order of selectivity can be used to estimate
the difficulty of converting the resin from one form to
another. Conversion from a highly selected to a less
highly selected form requires an excess of the new ion.
6
LIT212C 6/17/98 12:25 PM Page 6