Developing chambers:

The spotting may be done with a capillary tube or by use of a hypodermic syringe. However, mechanical dispensers with increased precision and accuracy are available commercially. After the sample solvent has evaporated, a plate is placed in a closed holder presaturated along with the developing solvent. Classical developing chambers used for ascending and horizontal thin layer chromatography are shown in Figure.

Figure:  Typical developing chambers used for (a) ascending and (b) horizontal thin layer chromatography.  In the later case, the sample is placed on both the sides of the plate and developed towards the centre

The plate is immersed in the developing solvent avoiding its direct contact. The developing solvent travels up the plate and after passing the point of sample application; it dissolves the sample and carries it up the plate. Thus, the sample distributes itself between the moving solvents and the stationary phase.

After the developer has traveled about two-third of the length of the plate, it is removed from the container and dried.