RP-Modified Silica Plates
Reversed-phase (RP) modified silica TLC plates provide additional selectivities and significantly broaden thin-layer chromatography applications. Hence, they are well suited for demanding TLC separations, and as a pilot technique for HPLC. RP-2, RP-8, and RP-18 plates are based on silica gel 60 modified with aliphatic hydrocarbons. The chain length, combined with the degree of modification, defines the plate’s ability to tolerate the water of the solvent system, and strongly affects retention. Using the same solvent system, migration time increases in the order: RP-2, RP-8, RP-18.
RP-2 TLC sorbents exhibit higher polarity and a high affinity to aqueous solutions, tolerating up to 80% water. In contrast, the longer carbon chains, RP-8 and R-18, can be run with up to 60% water in the solvent system.