Silica Thin Layer Chromatography Plate (TLC plate) is a commonly used analytical tool in fields such as chemistry and pharmacy, used for separating and analyzing the components of different substances. Thin layer chromatography (TLC) is a separation technique based on the differential distribution of substances between the stationary and mobile phases. The following are the basic steps of the experimental method for silica gel H-plate thin-layer chromatography:
Materials and equipment
SilicagelHTLCplate
Solvent system (mobile phase, usually solvent mixture)
sample solution
Spray reagent (such as ammonia, UV detector, etc.)
Development channel (such as glass channel)
Capillary tube (for sampling)
UV lamps or other color developing agents (such as iodine vapor, used for color development)
Pipette, graduated cylinder, etc
Experimental Procedure
1. Prepare TLC plates
When cutting silicone H-plates, a suitable size is usually chosen, commonly a small plate of 2.5cmx7.5cm.
Use a pencil to gently mark the starting line (usually 1-2cm from the bottom of the board), which is the spot where the sample is taken.
2. Prepare sample solution
Dissolve the sample to be analyzed in an appropriate solvent, with a concentration generally between 1-5 mg/mL. When using solvents, attention should be paid to their compatibility with the mobile phase.
3. Sampling
Carefully mark the sample solution on the starting line of the TLC plate using a capillary tube. When sampling, wait for the solvent to evaporate completely each time to avoid excessive sample.
Multiple samples can be sampled, but appropriate distance should be maintained between them to avoid incomplete separation.
4. Prepare development tanks and solvents
Add an appropriate amount of mobile phase (solvent) into the glass development tank. The selection of mobile phase should be based on the polarity of the target substance. Common solvent systems include mixtures such as n-hexane, ethyl acetate, chloroform, methanol, etc.
The liquid level of the solvent should be lower than the starting line of the TLC plate to prevent the sample from being dissolved by the solvent.
5. Development (Separation)
Place the TLC plate coated with the sample vertically into the development tank, ensuring that the bottom of the plate is immersed in the solvent but does not touch the sample point.
Let the solvent rise along the TLC plate and separate with the sample. When the solvent front rises to about the top of the plate, it stops developing.
If necessary, a condensing device can be used to maintain the solvent vapor in the tank, making the development process more uniform.
6. Remove and dry
Remove the TLC plate from the development slot and mark the position of the solvent front with a pencil.
Place the TLC plate in air or dry it in an oven to ensure complete solvent evaporation.
7. Testing
If the sample has UV absorption characteristics, the TLC plate can be directly irradiated with a UV lamp to observe the position of the separated spots.
If the sample does not have ultraviolet absorption, color reaction can be carried out by using color reagent spray (such as ammonia, iodine vapor, sulfur containing reagent, etc.).
By observing under color or ultraviolet light, different spots can be seen, and the movement speed (Rf value) of the spots can be used to identify the substance.
8. Analysis results
Measure the Rf value (spot migration distance/solvent front migration distance) of each separated spot, and analyze it by comparing the Rf values of known standard substances.
Precautions
Solvent selection: Choose the appropriate solvent system based on different substances to ensure good separation efficiency.
Sample size and accuracy: The sample size should not be too large to avoid incomplete sample dissolution or large spots that are difficult to distinguish.
Sealing of the development groove: Ensure good sealing of the development groove to avoid rapid solvent evaporation.
Experimental environment: During the experiment, excessive vibration and airflow should be avoided to avoid affecting the separation effect.
Through these steps, you can conduct thin-layer chromatography experiments using a silica gel H-plate, successfully separating and analyzing complex samples.