Bio-Rad Aurum Ion Exchange Mini Kits - Manual (Page 4)

columns have binding and elution buffers included to afford minimal handling
and ease of use. The formulations for each of the buffers are outlined in
Table 2.
Table 2. Properties of Bio-Rad ion exchange resins.
Aurum CEX Aurum AEX
Resin type UNOsphere S UNOsphere Q
cation support anion support
Binding capacity 12 mg IgG*/column 36 mg BSA*/column
Column bed volume 0.2 ml 0.2 ml
Binding buffer 20 mM sodium acetate, pH 5.0 20 mM Tris, pH 8.3
Elution buffer Binding buffer + 1.0 M NaCl Binding buffer+ 1.0 M NaCl
*Binding capacity determined using IgG (UNOsphere S) and BSA (UNOsphere Q). Capacity will differ
between proteins and will depend on the exact loading conditions.
A broad range of buffer systems can be used with Aurum AEX and CEX
columns, depending on the protein of interest or specific process required.
The chemical stability and broad operating pH range of the UNOsphere ion
exchange media allow the use of a variety of buffers. Buffers commonly used
for AEX or CEX can be used in place of the provided buffers (see Table 3).
The best results are achieved when buffering ions that have the same charge
as the functional group on the ion exchanger are used, e.g., phosphate paired
with a cation exchanger, or Tris paired with an anion exchanger. As a general
rule, the pH of the experiment should fall within the buffering range of the
chosen buffer (see Table 3). This permits use of the lowest possible buffer
concentration while maintaining maximum buffering capacity. In most cases,
a buffer concentration of 20 mM is recommended.
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