The automatic procedures for optimizing the composition of a binary mobile phase in reversed phase liquid chromatography have been intensively studied for the past ten years. The performance of these procedures, based on either the black box approach or on other methods such as the experimental design, are very often limited by the large number of time-consuming experimental runs that are necessary for the determination of the analysis conditions to be optimized.
The proposed method reduces this number of experiments: two experiments, run under linear variation of the composition of the binary mobile phase (the linear gradient elution mode), make it possible to determine the mobile phase composition corresponding to the maximum resolution between peaks, the final analysis being assumed to be camed out under isocratic conditions.
The method requires two steps: the determination of the retention characteristics for each solute, which depend upon the composition of the mobile phase; the selection of the optimum composition of the isocratic mobile phase, by using a criterion such as the maximum resolution normalized by the square root of the plate number, for the least separated pair of adjacent peaks.
The interest, performance and limits of use of such an optimization procedure are discussed by means of the chromatographic analysis of different complex mixtures.