Question

list three methods to detect colorless spots on a thin layer plate

Answer 1

The process whereby iodine visualizes otherwise invisible components of a developed thin layer plate has following points:

1. In this method a chamber of around 100 mL wide mouth jar (with

cap) is added a piece of filter paper and few crystals of iodine.

1. Iodine has a high vapor pressure for a solid and the chamber will rapidly become saturated with iodine vapor.

1. Now insert the TLC plate and allow it to remain within the chamber until it develops a light brown color over the entire plate.

1. If the compound has an affinity for iodine, it will appear as a dark brown spot on a lighter brown background.

1. Now remove the TLC plate Carefully and gently circle the spots with a dull pencil, because after some time iodine will not remain on the TLC plate

The visualization of organic compounds with Aluminium chloride

This is used for flavonoids in this process Spray plate with a 1% ethanolic solution of aluminum chloride as a result Yellow fluorescence apeares.

The visualization of organic compounds with Aniline phthalate

This is used For the detection of reducing sugars, in this method Dry the developed chromatogramSpray with 0.93g aniline and 1.66g o-phthalic acid dissolved in 100ml n-butanol saturated with water.

Then plate allow to dry with hot air, then heat to 105 C for 10 minutes

As a result Substance spots show different colors on an almost colorless background and Some spots also give fluorescence at 365nm.

The visualization of organic compounds with Ninhydrin / pyridine / glacial acetic acid

This is used For detection of peptide In this method , Spray with a 1% ninhydrin in pyridine/glacial acetic acid (5:1, v/v) Then plate allow to Heat 5 min at 100 C As a result Substance spots show blue color.