Figure 34.5: Tailing effect in thin layer chromatography.

A. Over-loading- if the sample is loaded much more than the loading capacity of the TLC plate, it appears as spot with trail or rocket shape spot. A diluted sample can be tested to avoid this.
 
B. Fluctuation in temp or opening of chamber- If there will be fluntuation in temperature or solvent saturation in the chamber (due to opening of the chamber during running), it disturb the flow of solvent front and consequently cause spot with trail. it can be avoided by maintaining a uniform temperature and the opening of the chamber should be minimized especially during running.

2. No movement of sample- In few cases, a sample doesn’t move from the spot after the run is completed. These problems are common with high molecular weight substances such as protein or chemicals with large number of functional group. In this case, a change in polarity or pH of solvent system can be explored to bring the compound into the solvent front so that it run on silica plate to get resolved.