Thin Layer Chromatography

Summary

In this video, you'll learn how to perform thin layer chromatography (TLC), a technique used to separate components of a mixture. The process begins with preparing the TLC plate, marking start and finish lines, and loading the sample using a micro capillary tube. The plate is then placed into a developing chamber with a solvent mixture. As the solvent moves up the plate, the different components of the sample separate. The video also covers troubleshooting tips, like using a UV lamp for colorless samples, ensuring effective resolution for clear results.

Takeaways

• 😀 Use the rough side of the TLC plate, which is coated in silica, for the experiment.
• 😀 Draw a line 1 cm from the bottom and another 5 cm above the first to mark the start and finish of the experiment.
• 😀 Draw the lines lightly to avoid scratching the silica off the TLC plate.
• 😀 Make a small tick mark at the center of the start line for each sample.
• 😀 Load the sample onto the TLC plate using a micro capillary tube by touching it to the surface of the sample.
• 😀 The sample will travel up the inside of the capillary tube due to capillary action.
• 😀 Use multiple brief touches with the micro capillary tube to keep the sample spot as small as possible for better resolution.
• 😀 Prepare the TLC chamber by adding 5 ml of solvent (usually a 7:3 mixture of hexane and acetone).
• 😀 Cap the chamber and let the gases reach equilibrium for several minutes before proceeding.
• 😀 Place the TLC plate into the developing chamber and cap it immediately to allow the solvent to move up the plate.
• 😀 Once the solvent line reaches the top line, remove the plate and let it dry on the bench top.
• 😀 If the sample is not colored, use a UV lamp to observe the spots.

Q & A

What is the purpose of using Thin Layer Chromatography (TLC)?

Thin Layer Chromatography (TLC) is used to separate the different components of a mixture, allowing for analysis of its individual parts.

Why is it important to use the rough side of the TLC plate?

The rough side of the TLC plate is coated with silica, which is essential for the separation of components in the mixture during the chromatography process.

What is the purpose of drawing lines on the TLC plate, and how far should they be from the bottom?

The lines on the TLC plate indicate the start and finish points for the sample. The first line should be drawn 1 cm from the bottom, and the second line should be 5 cm above the first.

Why should the lines on the TLC plate be drawn lightly?

The lines should be drawn lightly to avoid scratching the silica off the plate, which could interfere with the chromatography process.

How do you load a sample onto the TLC plate?

To load the sample, use a micro capillary tube. Simply touch the tip of the tube to the sample, and the sample will travel up inside the tube due to capillary action. Then, press the tube briefly against the TLC plate at the start line.

What should you do if the sample spot on the TLC plate becomes too large?

To keep the sample spot small and maximize resolution, it is best to make multiple brief touches with the micro capillary tube, rather than one large application.

What is the purpose of preparing a TLC chamber, and what solvent is typically used?

The TLC chamber is prepared by adding a solvent (typically a 7:3 mixture of hexane and acetone) to help the solvent move up the TLC plate during the experiment. The chamber is capped to allow gases to reach equilibrium before the plate is placed inside.

What should you do if you cannot see the solvent line during the experiment?

If you cannot see the solvent line, you can try shading the TLC chamber with one hand to improve visibility.

What happens when the solvent reaches the top line on the TLC plate?

When the solvent reaches the top line, the TLC plate should be removed from the chamber and set on the bench top to dry.

How can you observe the spots if the sample is not colored?

If the sample is not colored, you will need to use a UV lamp to observe the spots on the TLC plate.