Chromatographic Column

Quick Answer: A chromatographic column is a vertical glass tube with a controlled outlet at the bottom, packed with an adsorbent such as silica gel or alumina. A mixture loaded at the top is washed down with solvent, and its components separate as they travel at different speeds.

How the Separation Happens

Each component of the mixture divides its time between the stationary phase, the adsorbent in the tube, and the mobile phase, the solvent flowing through it. Polar compounds cling more strongly to polar silica or alumina and move slowly, while less polar ones move ahead. Collecting the eluate in a series of tubes, and checking the fractions by thin-layer chromatography, lets each component be recovered separately.

The classroom demonstration uses a coloured mixture such as the pigments extracted from spinach leaves, so students can watch a yellow-orange carotene band run ahead of the green chlorophylls. In synthesis the same technique purifies reaction products, sometimes with gentle air or nitrogen pressure at the top to speed the flow, which is known as flash chromatography.

The title does not state the length or internal diameter, the type of tap, whether a sintered disc or solvent reservoir is fitted, or whether the top has a ground joint. Those details decide how much sample the column can handle and whether pressure may be applied.

Care & Handling

• Pack the adsorbent as a slurry and never let the solvent level fall below the top of the bed; a dry bed cracks and channels.
• Protect the bed with a thin layer of sand, and add fresh solvent down the column wall so the surface is not disturbed.
• Apply gas pressure only to a column designed for it, keep the pressure low and work behind a safety screen.
• Tip spent silica into a solid waste container rather than rinsing it down the sink.

Specifications

Applications

• Separating plant pigments from a leaf extract in school and college practicals
• Purifying the products of organic synthesis on silica gel
• Separating dyes or indicator mixtures on alumina
• Clean-up of natural product extracts before analysis

Why Choose LabEquip

Teachers demonstrating chromatography and synthesis labs purifying products both use glass columns, often in more than one bore. LabEquip lists this column with its chemistry lab equipment, and a separating funnel can serve as a solvent reservoir above it; send the length and bore you need through the contact page.

Frequently Asked Questions

How is a chromatographic column packed?

Put a small plug of cotton or glass wool at the base unless the column has a sinter, add a layer of sand, then pour in a slurry of adsorbent in the starting solvent and tap the column gently so it settles evenly.

What is the difference between gravity and flash chromatography?

In gravity chromatography the solvent runs through under its own weight. Flash chromatography applies gentle gas pressure at the top to push solvent through faster, which needs a column and fittings suited to pressure.

Silica gel or alumina: which should I use?

Silica gel suits most neutral and acidic organic compounds and is the usual first choice. Alumina is useful for some basic compounds and is sold in acidic, neutral and basic grades.

How much sample can the column separate?

That depends on the bore of the column and how close together the components run. Chemists normally use many times more adsorbent than sample by mass, and more again for difficult separations.

How do I load the sample?

Dissolve it in the minimum of solvent and add it evenly to the top of the bed, or pre-adsorb it onto a little silica and add the dry powder. A narrow starting band gives sharper separation.

How are the separated fractions identified?

Collect the eluate in numbered tubes and spot each on a thin-layer chromatography plate. Tubes that show the same single spot are combined and the solvent is evaporated.

Last Updated: September 2026