Bio-Rad Bio-Rex® 70 Cation Exchange Resins - Manual (Page 5)

size and narrower size distribution ranges. Particle size is
given either in mesh size or micron size. Mesh refers to
the number of openings per inch on the screens used to
size ion exchange resins. Therefore, the larger the mesh
size, the smaller the particle size. Table 2 shows wet
mesh and equivalent micron diameters.
Table 2. Wet Mesh and Equivalent Micron
Diameters
Wet Mesh
(U.S. Standard) 16 20 40 50 80 100 140 200 270 325 400
Micron Diameter
(1 µ=0.001 mm) 1190 840 420 297 177 149 105 74 53 44 37
Large mesh material (20-50 mesh and 50-100 mesh)
is used primarily for large preparative applications, and
batch operations where the resin and sample are slurried
together. Medium mesh resin (100-200 mesh) is used
primarily in column chromatography, for analytical and
laboratory scale preparative applications. Fine mesh
material (200-400 mesh and minus 400 mesh) is used for
high resolution analytical separations.
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Bio-Rex 70 resin has a high capacity for
macromolecules, yet does not bind proteins so tightly
that they are difficult to elute. The acrylic polymer
matrix is hydrophilic, and generally free of nonspecific
binding or denaturing effects on proteins. Figure 1 shows
the titration curve. Note that the optimal operating pH
range is above pH 5.
Fig. 1. Bio-Rex 70 titration curve.
Bio-Rex 70 resin is available in several particle size
ranges. The flow rate in a chromatographic column
increases with increasing particle size. However, the
attainable resolution increases with decreasing particle
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meq. NaOH added per dry gram.
pH
Bio-Rex 70
LIT206B 6/17/98 3:07 PM Page 4