Column Chromatography Lab

Experiment 4: Thin Layer and Column Chromatography.

Name: Matthew Scully ID Number: 16188357

Date of the Experiment: 23rd of February 2018

Introducton:

Chromatography is used to separate a mixture into its different components and although there are different types of chromatography (e.g paper, TLC, column, size-exchange, etc.) they all rely on a mobile phase (which may be a gas or liquid) and a stationary phase (which may be a liquid or solid).

The first type of chromatography that we will use is TLC (thin-layer chromatography). TLC is very similar to paper chromatography, which is familiar from secondary school, except that instead of using

Unlike in TLC the different components can be separated and collected into different fractions. The stationary phase that we will use is aluminia (Al2O3), and as before the mobile phase will be the organic solvent chloroform:methanol (CHCl3/CH3OH). Similar to TLC, the mixture interacts with the solid and liquid phase and is brought down through the column by a flow of the mobile phase. Each component is carried down at a steady rate, which depends on the solubility in the mobile phase and how tightly it binds to the stationary phase, so that as the mixture is transported the components separate. The aluminia is very polar so polar components bind more tightly to it, this means that the higher up the fraction of the component that more polar that component is. The quicker a fraction reaches the bottom of the column, the less polar it

We placed a chromatography column in a retort stand and poured dry alumina powder into it until there was roughly 8cm of space from the top of the powder to the top of the column. We marked the position of the sand. Next, we let all the alumina flow into a beaker, to which we added CHCl3:CH3OH 5:1 until a slurry formed. The difficult part followed, we put the slurry into the open column, watching as the alumina settled and the solvent ran out of the column. Since the solvent ran out of the column faster than the alumina settled, we kept adding more solvent so that there was always solvent above the alumina. If the column had ran dry it could’ve cracked, which would cause the bands to run and mix. When the alumina had settled and reached the marked line, about 8cm from the top of the column, we closed the column. We then added close to a centimetres worth of sand, using a spatula, which served to prevent the disruption of the well-packed stationary phase when we added more solvent throughout the chromatography process. We then opened the column until the level of solvent was on the sand layer, then we added five drops of the 1:1 Sudan Red 111 and Victoria Blue R mixture. After that, we added solvent to fill up the column and then let it drain out, adding solvent constantly, making sure to let the solvent run down the side of the column to reduce its speed so as not to disturb the horizontal sand