Method and system for liquid choromatography separations

A method for automatically effecting liquid chromatography separations of a multicomponent sample using a mobile phase having three selectivity adjusting solvents and using a liquid chromatograph column having an automatic sampler module for introducing samples into the column comprising the steps of:

• selecting three solvents each contributing to a different one of the factors proton acceptor, proton donor, dipole interaction which contribute to total mobile phase selectivity along with a strength adjusting solvent for either reversed phase or normal phase chromatographic separations;
• effecting a chromatographic separation of the sample under a gradient condition which adjusts the strength of one of said three selectivity adjusting solvents with said strength adjusting solvent;
• calculating, based upon the retention time of the last sample component in the gradient run, the binary solvent composition E.sub.1 necessary to obtain the desired retention factor k' in an isocratic separation;
• calculating the equivalent mobile phase strengths for the remaining two binary solvent mobile phases;
• effecting successive separations of the sample and each component thereof utilizing the three defined solvents at their calculated strengths;
• utilizing blends of the fixed ratios of the three defined binary solvents to provide an overlapping resolution map and to determine the optimum mobile phase composition for obtaining a chosen selectivity;
• and
• effecting a sample separation using such optimum composition.