Bio-Rad Bio-Rex® 70 Cation Exchange Resins - Manual (Page 6)

the pH and conductivity of the effluent are the same
as that of the influent, the resin is fully equilibrated
and ready for sample application.
Section 4
Resin Conversion
Bio-Rex 70 resin can be converted to other ionic
forms by washing with a 0.5-1.0 M solution of the desired
counterion. Conversion to a counterion of relatively high
selectivity (see Table 1) will be rapid (2-3 bed volumes),
while conversion to a counterion of relatively low
selectivity will be slower (3-5 bed volumes). Conversion
is complete when the starting counterion is no longer
detected in the effluent. In most cases, this can be
monitored by pH or simple qualitative tests.
Section 5
Instructions for Use
Bio-Rex 70 resin may be used with either the batch
method or the column method. The batch method
consists of adding the resin directly to the sample and
stirring. The column method requires preparing a column
filled with resin, and passing the sample through.
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Section 3
Resin Equilibration
Especially when Bio-Rex 70 resin is used to separate
multi-component samples, it is very important to
equilibrate the resin to the initial buffer conditions before
the sample is applied. In general, unequilibrated resin
will not give reproducible results. Due to its weakly
acidic functional groups. Bio-Rex 70 resin is slow to
equilibrate. The following procedure is recommended:
1. Place the Bio-Rex 70 resin in a beaker with the
buffer in which it is to be equilibrated. The volume
of buffer should be four to five times the volume of
the resin.
2. Allow the resin to equilibrate for at least 30 minutes.
Adjust the pH with acid or base. Re-equilibrate.
Repeat until pH is stable.
3. When pH is stable, decant the buffer off and repeat
steps 1 and 2 using fresh buffer. Repeat until no pH
change is noted when fresh buffer is added. This may
take several buffer changes.
4. Decant excess buffer off and pour the resin into the
column. Pass 2-3 bed volumes of buffer through the
column, monitoring both pH and conductivity. When
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LIT206B 6/17/98 3:07 PM Page 6