Selectivity Optimization with Commercial Coupled Columns by Gradient Stationary Phase Optimized Selectivity Liquid Chromatography

In previous studies stationary phase optimized selectivity liquid chromatography (SOSLC) has been already proved as a promising technique to optimize the selectivity of a given separation [1, 2]. By combination of different stationary phases, SOSLC offers excellent possibilities for method development under both isocratic and linear gradient conditions. However, the so far available commercial SOSLC protocol utilizes specialized column cartridges and corresponding cartridge holders to build up the combined column of different stationary phases. The present work is aimed at developing and extending the SOSLC approach towards more widely available commercial stationary phases and therefore to more convenient application by substituting the specialized column cartridges from Bischof Chromatography by generic connection pieces to connect short commercial HPLC columns. Instead of the retention time difference between the critical pair, the selectivity factor (α) is thereby used as the target in the process of stationary phase optimization in order to obtain baseline resolution of all target solutes under a given gradient profile. The SOSLC principle is illustrated with a fast, full baseline resolution for a randomly selected mixture composed of phenones, benzoic acids and benzoates. The average correlation coefficients between the predicted and experimental retention times are shown to be above 0.999 and the average standard deviation between the predicted and experimental selectivity factor α is less than 0.01. This contribution further broadens the applicability range of the priory developed gradient SOSLC software [1].