Bio-Rad AG® MP-1M Anion Exchange Resins - Manual (Page 9)

using 20 bed volumes of 1 N NaOH. The resin has a
very low selectivity for hydroxide, making the conver-
sion to the formate form relatively simple (2 bed vol-
umes of 1 N formic acid). Another conversion method is
to first convert to an ionic form of intermediate selectiv-
ity. When converting from the chloride form (relative
selectivity 22) to the hydroxide form (relative selectivity
1), the resin can first be converted to the bicarbonate
form (relative selectivity 6.0).
The easiest method to test for completeness of con-
version depends on the particular conversion.
Conversion is complete when the first ion is no longer
detected in the effluent. In many cases, this can be moni-
tored by pH or by simple qualitative tests. When conver-
sion is complete, the resin should be rinsed with deion-
ized water, then with starting buffer, until a stable pH is
obtained. The resin is then equilibrated to the desired
starting conditions.
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Conversions to ionic forms not listed in Table 5 can
be achieved using the information supplied in Table 3,
which lists relative selectivities of various counterions
for AG 1, AG MP-1, and AG 2 resin. To convert a resin
to an ionic form with a higher selectivity, wash the resin
with 2-5 bed volumes of a 1 M solution of the desired
counterion. For conversion to an ionic form with a lower
relative selectivity for the resin, the necessary volume of
counterion solution will depend on the difference in
selectivity. As a general rule, use 1 bed volume of 1 M
counterion solution for each unit difference in relative
selectivity. For example, converting AG 1-X8 resin
from the formate form (relative selectivity 4.6) to the
hydroxide form (relative selectivity 1.0) would require
4-5 bed volumes of 1 M NaOH.
In some cases, it is more economical and more effi-
cient to go through an intermediate counterion when
converting to a counterion of much lower selectivity.
One example of this is the conversion of AG 1-X8 resin
from the chloride form (relative selectivity 22) to the
formate form (relative selectivity 4.6). The resin is first
converted to the hydroxide form (relative selectivity 1.0)
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LIT212C 6/17/98 12:25 PM Page 12