Abstract: The invention relates to a method for controlling preparative liquid chromatography, comprising the following steps, at least a part of said steps being implemented by a computer comprising a processor and a display screen coupled to said processor: (a) selecting an analytical liquid chromatography method from among thin layer chromatography (TLC) and high performance liquid chromatography (HPLC), (b) inputting analytical liquid chromatography data obtained by the method selected at step (a) for a product to be purified, (c) accessing a table of separating tools available to the user to implement said preparative liquid chromatography, (d) from said analytical liquid chromatography data and table of available separating tools, selecting an optimal separating tool from said table and computing preparative liquid chromatography operating conditions for said selected separating tool.