Characterization and prediction of retention in gradient-elution normal phase HPLC with ternary gradients

Chromatographic behaviour of phenylurea herbicides and phenols on a silica gel column with ternary gradient elution using mobile phases containing dry 2-propanol, n-heptane and dioxane was investigated. With dried solvents and the temperature controlled to ±0.1 °C, the data from repeated experiments measured on the same column after ten months of use were reproducible. Algorithms were suggested for characterization and prediction of retention in ternary gradients at a constant ratio of the two polar solvents (elution strength gradients) and at a constant sum of their concentrations (selectivity gradients). These were based on two- and three-parameter equations describing the dependence of the sample retention factors (isocratic) on the concentration of the polar solvent in binary mobile phases.