Thin Layer Chromatography

Merck Millipore TLC plates have been developed for reliable routine analysis of a broad range of substances in pharmaceutical, environmental, food and beverage analysis. They are available in base formats (e.g. 20 x 20 cm), backed in either, glass, aluminum or plastic, with or without a fluorescent indicator.

Within the entire product range, unmodified silica is the most widely used sorbent in TLC, enabling the analysis of nearly any substance if the appropriate mobile phase is chosen. It covers nearly 80% of thin layer applications for both adsorption and partition thin layer chromatography. The classical silica TLC plates are based on proven Merck Millipore silica gel 60 with a pore diameter of 60 Å, a pore volume of 0.8 ml/g and a specific surface of 520 m²/g (BET). The unique polymeric binder results in a very adherent and hard surface that will not crack or blister; it even allows you to write on the surface with a pencil, without risking damage to the layer. The smooth, dense plate surface guarantees sharp bands for maximum separation efficiency with lowest background noise when performing scanning densitometry.

For specific TLC applications, the following modifications of the stationary phase could be successfully used. These are:

• Aluminum oxide TLC plates

Merck Millipore TLC aluminum oxide plates utilize neutral or basic aluminum oxide of 60 Å or 150 Å pore size with or without a fluorescence indicator to suit different application needs. Aluminum oxide plates provide distinct separation features with regard to the pH range used. Under aqueous conditions basic compounds can be best separated on basic aluminum oxide plates, while neutral compounds are best separated on neutral plates.

• RP- and NH₂-modified TLC plates

RP-modified silica layers are well suited for many separation problems that cannot be sufficiently solved by unmodified silica, e.g. separation of extremely non-polar and highly polar substances using aqueous solvent systems. Furthermore, the chromatographic behavior of these plates is less dependent on atmospheric humidity. In contrast to unmodified silica, RP-phases do not exhibit catalytic activity and are therefore the plates of choice for instable substances that might tend to oxidative degradation.
Merck Millipore TLC plates RP-2, RP-8 and RP-18 are based on silica gel 60 modified with aliphatic hydrocarbons of increasing hydrocarbon chain length resulting in increased hydrophobic properties.
Amino-modified TLC NH₂ plates provide weak basic ion exchange characteristics. These unique features enable for the separation of charged compounds such as nucleotides, purins, pyrimidines, phenols and sulfonic acids using simple eluent mixtures. In addition, NH₂- modified silica plates allow for reagent free detection of certain chemical substances by thermochemical fluorescence activation.

• Cellulose TLC plates

Cellulose is an organic sorbent that is particularly suitable for the separation of hydrophilic substances by partition chromatography. Classical TLC cellulose layers are based on a microcrystalline cellulose for standard separations. They are available either backed in glass, aluminum or plastic, with or without fluorescence indicator. Typical applications of cellulose include the analysis of amino acids, carbohydrates, phosphates, nucleic acids and nucleic acids derivatives.