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To choose silica gel for column chromatography, work from the molecule you are separating. Match the pore diameter to the size of that molecule first, then choose a particle size that gives the resolution and flow rate your column needs. In our range that means choosing between the XCL-A, XCL-B and XCL-C grades by pore structure, or moving to macroporous or microsphere silica for larger molecules and carrier duties. This page sets out what each grade is for and exactly what to write on the order.
Our column chromatography silica gel is a white powder whose main component is SiO₂·nH₂O. It is supplied in industrial and reagent grades, differentiated by pore structure. This is the first selection decision.
| Property | XCL-A | XCL-B | XCL-C |
|---|---|---|---|
| Pore diameter (Å) | 20–40 | 50–80 | 80–100 |
| Pore volume (ml/g) | 0.35–0.5 | 0.5–0.75 | 0.8–1.0 |
| Specific surface area (m²/g) | ≥ 600 | 400–600 | 300–400 |
| Chlorides (reagent grade) (%) | ≤ 0.02 | ≤ 0.02 | ≤ 0.02 |
| Iron (reagent grade) (%) | ≤ 0.02 | ≤ 0.02 | ≤ 0.02 |
If your molecules are large, a narrow-pore gel excludes them from most of its surface. Two alternatives give them more room. Our macroporous chromatography silica gel is a reagent-grade white granular material with a pore volume of 1.00–2.00 ml/g, an average pore diameter of 10–18 nm and a specific surface area of 200–320 m²/g; particle size is 2–250 µm and is customisable. Beyond separation it also serves as a medicinal flow aid, a catalyst, enzyme and inorganic-adsorbent carrier, and a protective-bed desiccant. Our coarse pore microsphere silica gel has a pore volume of 0.80–1.30 ml/g, a pore size of 80–120 Å and a surface area of 300–550 m²/g, and is used for petrochemical catalysts and carriers and for selective adsorption of organic gases and liquids.
The rule behind every silica grade is the same: the pore structure must fit the molecules you are separating. A small-pore, high-surface-area gel gives more adsorption sites for small compounds — but a molecule too large for the pore is excluded from most of that surface. For bigger molecules, choose the coarser XCL-C grade, a macroporous grade, or the microspheres, and let the molecule reach the surface instead of being shut out of it.
Particle size sets the trade between resolution and flow: smaller particles pack a tighter bed and resolve closer peaks but raise back pressure, while larger particles flow freely and flatten the separation. For the XCL grades, particle size (mesh) is set on agreement with your requirement rather than a single fixed figure, so state the column dimensions, the flow rate and the resolution you need and the grade and particle size are matched to it. If your priority is speed, our dedicated guide on flash column chromatography silica gel covers how particle size and flow rate pull against each other.
The mixture you are separating, the column and flow rate, and the resolution you are targeting are the three answers that let us recommend a grade. Prices are quoted on request.
For the flat-bed formats, see our TLC silica gel and TLC plates, and what to specify for TLC and H plates. For the wider selection logic behind these grades, read our overview Silica Gel for Column Chromatography.
Send your separation detail and column setup — we will match the grade, pore size and particle size and quote it.
