Chromatography Silica Gel Grades Compared: 60Å vs 100Å, 40–63µm vs 63–200µm

Chromatography silica gel grades are defined by two numbers: pore diameter — most often 60 Å or 100 Å — and particle size, most often 40–63 µm (230–400 mesh) or 63–200 µm (70–230 mesh). A 60 Å gel has the higher specific surface area and suits small molecules; a 100 Å gel opens the pores to larger molecules. A 40–63 µm powder packs a tighter bed for flash columns and sharper bands; a 63–200 µm powder flows faster under gravity alone. Below is how the common chromatography silica gel grades compare, and what to put on the order.

The Two Numbers, and Why They Are Separate Choices

Pore diameter is the width of the internal channels inside each particle. It controls which molecules can reach the adsorption surface and how much of that surface they can use, so it is chosen against the size of the molecules you are separating. It is quoted in ångströms (1 Å = 0.1 nm), and the two workhorse grades are nominal 60 Å and 100 Å.

Particle size is the diameter of the powder grains themselves. It controls the flow of mobile phase and the sharpness of the bands, so it is chosen against the column, the pressure you can apply and the resolution you need. It is quoted in micrometres (µm) and, on many data sheets, in US sieve mesh — the two describe the same powder, so a grade sold as 40–63 µm is the same as 230–400 mesh.

60 Å vs 100 Å Pore Diameter

The pore diameter sets the surface area, and the surface area sets how much of the packing a molecule can interact with. Narrower pores mean more surface per gram but smaller openings; wider pores trade some surface for room for larger molecules.

Read the table as orientation, not as a certificate. Surface area and pore volume are typical supplier values and move a little from batch to batch, which is why the grade is defined by the nominal pore diameter and the actual figures are confirmed on the certificate of analysis. If your molecules are large — many natural products and macromolecules — the practical alternative to a wider-pore powder is a dedicated macroporous chromatography silica gel or coarse pore microsphere silica gel, where the pore is large by design rather than by grade.

40–63 µm vs 63–200 µm Particle Size

Particle size is the flow-rate decision. Smaller particles pack a tighter, more even bed with less band spreading, so close-running compounds separate more cleanly — but they raise back pressure and need either a pump (flash) or patience (gravity). Larger particles open the gaps between grains, cut back pressure and let the mobile phase run faster, at the cost of broader bands.

For finishing purities rather than preparative runs, the flat-bed formats use a different granularity again — our guide to silica gel TLC plates and H plates covers that side. And if you are specifying a running column from scratch, the packing procedure matters as much as the particle size, so see how to pack and run a silica gel column.

Where These Grades Sit in Our Range

Our column chromatography silica gel is supplied in the XCL-A, XCL-B and XCL-C pore grades with the particle size (mesh) set to your requirement, so a 60 Å or 100 Å-style behaviour can be matched to the separation rather than fixed by a single catalogue number. Where the pore arrangement is the limiting factor rather than the particle size, the macroporous and microsphere grades above give the wider, more accessible pore structure that large molecules need. The full laboratory line is listed under Chromatography & Lab.

How the Grades Differ From Desiccant Silica

A chromatography grade is not the same product as the silica gel in a sachet, even though both are silicon dioxide. The pore structure, the particle-size specification, the cleanliness and the metal limits are set for separation, not for moisture uptake. We explain the difference in chromatography silica vs desiccant silica, which is worth reading before you assume a bulk desiccant grade will do.

What to Put on the Order

• Pore diameter — nominal 60 Å, 100 Å, or a macroporous / microsphere grade for large molecules.
• Particle size — 40–63 µm (230–400 mesh), 63–200 µm (70–230 mesh), or your own mesh range.
• Grade class — industrial or reagent, by the purity your work needs.
• Quantity and packing — the XCL grades ship in a 20 kg composite bag; other packaging is available on request.

Give us the mixture, the column and the resolution you need, and we will match the pore diameter and particle size and quote the quantity. Prices on request.

Sources and Standards

The figures above are typical values from chromatography-grade silica gel supplier data sheets and are reported against the usual test methods. Where a standard is named, the standard number is given:

• Pore-size classification (micro-, meso- and macropore) follows the IUPAC definitions — micropore below 2 nm, mesopore 2–50 nm, macropore above 50 nm.
• Particle-size fractions are sieve fractions; the mesh equivalent follows ASTM E11 (woven wire test sieve cloth).
• Specific surface area is measured by gas adsorption using the BET method, ISO 9277.
• pH is quoted from a dilute aqueous suspension, the method printed on the supplier data sheet.