Mesh & Sieve
If you know the mesh range of your beads or packing, you can get the nominal particle size. Many column packings are 200 - 400 mesh, corresponding to 37 - 74µm, and are sometimes called out as 40 µm. This means that a frit with a pore size of 16 - 40 µm will not clog when used to support a nominal 40µm packing. Peptide synthesis beads are typically 100 - 200 mesh, which would translate to 74 to 149 µm. Our understanding of real life is that there can be considerable statistical variation in bead size depending on the manufacturer. See photos below.
Mesh and sieve opening relations are shown below.
| Mesh # |
Sieve opening, µm
|
|---|---|
| 400 |
37
|
| 200 |
74
|
| 170 |
88
|
| 140 |
105
|
| 100 |
149
|
| 80 |
177
|
| 60 |
250
|
| 40 |
420
|
(US Standard ASTM 11-61)
The following series of photos illustrates the changing relationship between peptide resin beads and frit. The red-dyed resin beads remain constant to the increasing frit porosity. With the extra coarse frit, you can see that the beads begin to snuggle between the glass particles, clogging the pores. Thanks to Dr. Ron Zuckermann, now with the Molecular Foundry at Lawrence Berkeley Laboratory, for his help with this series.
|
Medium porosity frit: 10-15 µm |
 |
|
Coarse porosity frit; 40-60µm |
 |
|
Extra coarse; 170-220µm |
 |
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