^#.^t1: Overview of Drug Analysis and Structure of the Book
Thin layer chromatography (TLC) can be used in a very broad context in drug analysis. It is a separation technique in which the separation process occurs in a uniform planar layer of sorbent placed on a glass or aluminum plate or plastic sheet. The sorbent is called the stationary phase. During analysis, the plate is immersed in the mobile phase, generally a mixture of two to four solvents, and developed vertically or horizontally. The separation process occurs due to various mechanisms such as adsorption (e.g., hydrogen bond interactions), partitioning between the stationary and mobile phases, or ion exchange, depending on the nature of the sorbent. After development, compounds can be detected (visualized) and identied by their natural color or uorescence, quenching of uorescence on a layer containing a uorescent indicator, or by creating colored spots after treating the plate with a chromogenic detection reagent by spraying, dipping, or exposure to vapors. The main reason for continuous high interest in TLC is that it does not require any complicated equipment, and commercially available plates can be developed in almost any laboratory.