Screening of Complex Natural Extracts by Countercurrent Chromatography Using a Parallel Protocol

In countercurrent chromatography (CCC) the choice of the liquid system is the heart of any separation. It corresponds to the selection of the mobile phase and the stationary phase at the same time. Any change in one phase composition induces a change in the other phase composition which renders the choice of the appropriate liquid system difficult and lengthy. A scale of compositions of the heptane−ethyl acetate−methanol−water quaternary liquid system was referred to by letters from A to Z and called the Arizona (AZ) liquid system. Each composition of the AZ system has the same heptane/ethyl acetate and methanol/water volume ratios. It is shown that there is a continuous polarity change from the hydrophilic A composition (ethyl acetate−water) to the hydrophobic Z (heptane−methanol) mixture by measuring the distribution constant KD of a known test mixture. For all compounds, the log KD is linearly increasing with the water content of the lower aqueous phase of the composition used. The slopes of the log KD...