Forced flow solvent demixing

Jost et al. (212) studied the use of TLC as a pilot technique for transferring retention data to column LC (HPLC). TLC is potentially an inexpensive and convenient method for this purpose if essentially identical phases with the same retention mechanisms are used. However, there are inherent procedural differences in TLC and HPLC, which make exact transfer of data questionable. These differences include a capillary mobile phase driving force in TLC, and forced flow with constant and adjustable rates in HPLC formation of mobile phase gradients (solvent demixing) when multicomponent solvents are used in TLC preloading of the stationary phase with components from the gas phase of the TLC solvent and the presence of binder in layers but not columns. 

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