TLC is an acronym for Thin Layer Chromatography. It’s called Thin Layer because the stationary phase is formed into a thin layer coated onto an inert backing material which can be rigid or flexible. A typical rigid backing is glass, and flexible backings can be either plastic or aluminum. Coatings on a rigid backing are usually referred to as TLC plates whereas those on a flexible backing are referred to as TLC sheets.

Chromatography is the science of separation of things in a mixture. It is a multi-phase system with a stationary phase, a moving phase, and a phase in which the analyte mixture is separated. The stationary phase, as its name implies, is fixed in place. The moving phase, also called the mobile phase, moves past the stationary phase. The analyte components interact with the two phases to different degrees. This differential interaction results in a physical separation of the components of the mixture.

Chromatography can be subcategorized in various ways. If the moving phase is a liquid, it is called Liquid Chromatography or LC. If the moving phase used is a gas, it becomes Gas Chromatography or GC. Liquid Chromatography operated under high pressure is called High Pressure Liquid Chromatography or HPLC.

The distinction might be based on the type of analyte being analyzed, such as Ion Chromatography. The name could reflect the form of the stationary phase, such as a thin layer, hence Thin Layer Chromatography or TLC. Or the name could derive from the mechanism of the interaction between stationary and mobile phase, such as Size Exclusion Chromatography.

HPTLC is an acronym for High Performance Thin Layer Chromatography. It is a form of TLC utilizing a smaller particle adsorbent, which improves resolution.

High Performance plates are also smaller in size, typically 10×10 cm or even 5×5 cm. Smaller plates necessitate shorter development distance, which means quicker development times.

HP plates also consist of a thinner coating layer than analytical TLC plates. HPTLC layer thickness is typically 150-200 microns, versus 250 microns for standard TLC plates.

A thinner coating requires a reduction in the sample size. Sample sizes begin to range into nanoliters of applied sample versus microliters for analytical plates. Larger sample volumes must be divided into aliquots during sample application.

The combination of smaller particle adsorbents with tighter distribution, thinner coatings and shorter development distances, along with smaller sample size combine to decrease diffusion and improve performance. The result is an increase in resolution and detectability of the sample components.