Developers

For chromatography, a developer is a reagent that is used to give color to a colorless substance. A developer may also be called a stain, a developing reagent, or a dyeing reagent. Most developers are destructive and react with the substance on the paper or plate. The use of a developer helps locate spots on a piece of paper or a TLC plate.

The most commonly used developer in paper chromatography is iodine. Iodine is a semi-destructive developer because the iodine will eventually evaporate off the TLC plate and leave the original compound. To apply the developer, the chromatogram can be sprayed with the reagent or placed in a developing chamber that contains the reagent. In the case of iodine, the developing chamber would contain a few iodine crystals.

An example of the developer ammonium sulfide being used in an experiment can be seen here.

References:

• NCERT Chromatography handbook

• Chemistry Libre Texts, Organic Lab Techniques, Chromatography, TLC, Visualising TLC Plates, written by Prof. Lisa Nichols, accessed on 11^th Feb 2021