The distance from the bottom pencil line to the center of a substance spot is the distance of advance of the substance. The ratio of substance advance distance to solvent advance distance is the R f value for the substance. The figure shows a developed plate for a mixture consisting of 4 components with Rf values of about 0.05, 0.2, 0.5, and 0.9 TLC of Inks . Before attempting to apply TLC to the challenging problem of separating and identifying amino acids, it is advisable to learn and practice the technique by applying it to mixtures that are easily visualized and separated. Inks provide an ideal practice vehicle for TLC because they normally contain several colored components that separate nicely in common solvents such as ethanol, acetone, or chloroform.
Inks are of different types and colors, of course.
Different types require different solvents for development. Common sources of ink are ball point pens, felt-tip markers, and roller ball pens. Bottled ink is still available for people using fountain pens. You should select inks from at least 2 different sources available in the lab and should find a solvent or mixture of solvents that separates each ink into its component colors. Experimental Procedure .