Chemistry · Ch 3 — Some Analytical Techniques
Column Chromatography
Column Chromatography
Setting Up the Column
In Column Chromatography, the separation takes place over a column of stationary-phase material — commonly alumina or silica gel. A slurry of this material is packed into a long glass tube fitted with a stopcock at the bottom and a plug of glass wool at the lower end (to hold the packing in place). The mixture to be separated is first dissolved in a small amount of a suitable solvent and loaded onto the top of this packed adsorbent column. A suitable mobile phase — a single solvent or a mixture of solvents — is then poured over the column and allowed to slowly move down through it, carrying the mixture along.
How the Bands Form …
What this figure shows. A long vertical glass tube with a stopcock at the bottom and a glass-wool plug just above it, packed with a slurry of stationary-phase adsorbent (alumina or silica gel); the mixture, loaded at the top of this packed column, is shown at successive stages as the mobile phase carries it downward, separating into horizontal bands stacked at different heights within the column — the most strongly adsorbed component's band staying nearest the top (moving least) and the more weakly adsorbed components' bands lying progressively lower, with the most weakly held component closest …