Apparatus and Requirements:

Commonly, the plates in sizes of 2.5×10, 2.5×15, 2.5×20, 5×20, 10×20, and 20×20 in centimeters are available. These are of two kinds: conventional and high-performance. The former have thicker layers of about 0.25 mm along with particle size of < 20 µm. Instead, the high performance plates usually have thickness of 0.1 mm and particle size of <5 µm. As the name denotes, high performance plates provide fast and sharp separations. In terms of plate theory, the conventional TLC will have about 2000 plates in 12 cm with development time of less than 30 minutes. Correspondingly, the number of plates in high-performance TLC will be about 4000 in 3 cm requiring 10 minutes development time. Therefore, the high performance TLC has much less sample capacity.

The sample application in TLC is the most critical aspect and particularly so in quantitative measurements. Commonly the sample is dissolved in an appropriate solvent with a concentration of less than 0.1% and applied as a spot of about 1 cm from the edge of the plate. The spot should be as small as possible and dried in a manner similar to PC. In case of dilute solutions, 3 to 5 drops are applied.