I believe that they did not start with TLC as TENDER, LOVE and CARE but one thing that the Scientists called Thin Layer Chromatography. Everything began when one had an idea to coat a glass plate with silica gel and then after apply a small drop of sample  one solvent was used to run up the glass plate by capillarity.
Look carefully each figure below and You will be able to understand such technique that is simple and do not needs so much skills.

The solvent by capillarity goes up  In Thin Layer Chromatography the solvent or more known as Mobile Phase is a Non Polar substance such as Ethyl Acetate. The Stationary Phase is Polar because it consist of Silica that is Polar.

Finally the silica plate with samples is take off from the TLC Chamber  and dry at room temperature.
Note: Such Operation Must Be Done in a Fume Hood to Avoid the Chemical Fumes that are Health Hazardous.
The revelation is done in generall with Ultra Violet light because most the Pharma Products contain Amines (NH₂).

The name says a lot. Reverse Phase Chromatography because now the Stationary Phase is Non Polar and the Mobile Phase is Polar or Moderately Polar.

Let's to analyse the Mobile Phase:

        Aqueous     +   Organic

 H₂O that is highly polar but weaker solvent.
Organic modifier that can be Methanol (MeOH); Acetonitrile (ACN) and Tetrahydrofuran (THF).
Once the Polarity of Solvent Decreases, the Solvent Strength Increases. Consequently 52% Methanol = 48% Acetonitrile = 32% Tetrahydrofuran.
 

 
 
 
 
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