Question

Thin layer chromatography (tlc)

Questions 1. List three factors that affect R¢ values in adsorption TLC. Explain. 2. Explain how to prepare sample solutions and capillary applicators. 3. Describe the basic principle underlying all chromatographic processes.

Answer 1

1. Factors affecting Rf value in adsorption TLC :

* Adsorbent Nature : Stronger compound is bound to adsorbent and runs up slowler on TLC plate. Polar compounds runs up slowly while Non polar compounds runs rapidly on TLC plate.

* Mobile phase : There is interaction between mobile phase and stationary phase. If polarity of mobile phase increases then interaction with stationary decreases. Higher polarity of mobile phase increases the Rf value.

* Temperature : Temperature of solvent and TLC plate can make changes in Rf value.

2. Preparation of sample solution and capillary applicator :

Take small amount of sample (2-3 mg) in sodium fission tube and dissolve suitable solvent (1-2 mL).

To prepare capillary applicator hold the capillary on burner as it devides in two equal parts and stretch it you will get narrow end. Hold the narrow end of capillary applicator in sample solution it will come up in the applicator by capillary action.

3. Basic Principle of chromatography :

It is a method of separation of components of sample between two phases i.e. Stationary phase and mobile phase.

Components are separated on their differential distribution between two phases.

Substances moves with mobile phase on different rate depending on their partition coefficient.

Stationary phase may be solid, liquid, or gas and mobile phase may be liquid or gas, never be solid .