Technique
The process is similar to paper chromatography with the advantage of faster runs, better separations, and the choice between different stationary phases. Because of its simplicity and speed TLC is often used for monitoring chemical reactions and for the qualitative analysis of reaction products.
To run a thin layer chromatography, the following procedure is carried out:
- A small spot of solution containing the sample is applied to a plate, about 1.5 centimeters from the bottom edge. The solvent is allowed to completely evaporate off, otherwise a very poor or no separation will be achieved. If a non-volatile solvent was used to apply the sample, the plate needs to be dried in a vacuum chamber.
- A small amount of an appropriate solvent (elutant) is poured in to a glass beaker or any other suitable transparent container (separation chamber) to a depth of less than 1 centimeter. A strip of filter paper (aka "wick") is put into the chamber, so that its bottom touches the solvent, and the paper lies on the chamber wall and reaches almost to the top of the container. The container is closed with a cover glass or any other lid and is left for a few minutes to let the solvent vapors ascend the filter paper and saturate the air in the chamber. (Failure to saturate the chamber will result in poor separation and non-reproducible results).
- The TLC plate is then placed in the chamber so that the spot(s) of the sample do not touch the surface of the elutant in the chamber, and the lid is closed. The solvent moves up the plate by capillary action, meets the sample mixture and carries it up the plate (elutes the sample). When the solvent front reaches no higher than the top of the filter paper in the chamber, the plate should be removed (continuation of the elution will give a misleading result) and dried .
Read more about this topic: Thin Layer Chromatography
Famous quotes containing the word technique:
“The mere mechanical technique of acting can be taught, but the spirit that is to give life to lifeless forms must be born in a man. No dramatic college can teach its pupils to think or to feel. It is Nature who makes our artists for us, though it may be Art who taught them their right mode of expression.”
—Oscar Wilde (1854–1900)
“I cannot think that espionage can be recommended as a technique for building an impressive civilisation. It’s a lout’s game.”
—Rebecca West (1892–1983)
“The more technique you have, the less you have to worry about it. The more technique there is, the less there is.”
—Pablo Picasso (1881–1973)