Question

Thin Layer Chromatography (TLC) polarity questions

Is silica gel polar or non polar and why? How do different solvents with different polarities cause different elution patterns on a TLC slide? What causes substances to separate as they move up a TLC slide?

Answer 1

Silica gel is polar nature. it is a polymer of -(Si-O-Si)- it has electronegative Oxygen atom. if an organic compound has polar groups such as -OH, -NH2 will bind tightly with silica gel. Hence it will be eluted only with strong polar solvents like CH3OH, CHCl3 etc.,

TLC slide works with the principle of mobility or capilliary action of atoms or groups.compounds with no polar groups like alkene, benzene etc., will have greater mobility than compounds has polar groups like -OH, -NH2 for example phenol aniline etc.,so Rf value will be higher for non polar compounds than polar compounds.