Thin layer chromatography is, surprise surprise, a type of chromatography. Previously on the channel, we have covered a lot of other chromatographies. All of them have a few things in common:
1. They separate mixtures of substances into their constituent components
2. They all have a stationary phase and a mobile phase
3. The mobile phase flows through the stationary phase and carries the sample with it
4. Different components in the sample will travel at different rates, due to how they interact with the stationary phase, thereby separating them
Basically it is similar to 2 cars on a highway, traveling in the fast lane and the slow lane. Even if the cars start at the same position and time, after a certain amount of time they will have separated from another due to the speed at which they travel. A simplified version but hopefully effective to demonstrate the principle for you!
Now, let us take a look at what this looks like in reality! So here we have a very basic setup for a thin layer chromatogram. A pencil line has been drawn near the bottom of the TLC plate and a small drop of sample solution placed on this line and marked. The plate is then placed inside a beaker with a small amount of solvent in it. Note, that it is important that the level of solvent is below that of the sample drop. Due to capillary action, the solvent will begin to move up the plate and take the sample with it. As the solvent slowly travels up the plate, the different components of the dye mixture travel at different rates and the mixture is separated into different spots. The solvent is allowed to rise until it almost reaches the top of the plate, giving the maximum separation of the components of the sample. At that point the, the plate gets removed from the beaker and the position of the solvent is marked with another line. Finally, please remember to like this video to help it spread to other people who could find it useful! That might be the most important step in TLC after all!
These different lines can be used to calculate something called the Rf value, which help us identify what compounds are present in the sample. This Rf value is calculated by using the formula: Rf = distance traveled by component/distance traveled by solvent.
But what makes these compounds separate differently from each other in the first place? Well, mainly two things:
1. How soluble the compound is in the solvent, which depends on how much attraction there is between the molecules of the compound and those of the solvent.
2. How much the compound sticks to the stationary phase, which depends on how much attraction there is between the molecules of the compound and the silica gel.
But why is this useful? Well, the reason why chromatographies like TLC are so useful is that it allows us to easily and efficiently separate different compounds from each other in a solution. This means that TLC can be used in order to:
- identify compounds
- determine their purity
- follow the progress of a reaction
9 сен 2024
