Rapid optimization of dual-mode gradient high performance liquid chromatographic separation of Radix et Rhizoma Salviae Miltiorrhizae by response surface methodology.

An approach for rapid optimization of dual-mode gradient high performance liquid chromatography (HPLC) by response surface methodology (RSM) was developed for fast simultaneous separation of hydrophilic and hydrophobic components in Radix et Rhizoma Salviae Miltiorrhizae (Danshen) and its preparations. The aim of this study was to achieve a high throughput RSM optimization using a short ultra-high performance liquid chromatographic (UHPLC) column to simultaneously optimize flow rate and solvent gradient, and then transfer the optimized method to conventional HPLC for routine analytical purposes. The optimization was designed with Box Behnken design (BBD) and the global Derringer's desirability was used for describing the multicriteria response variables. Sixty-two designed experiments were performed by UHPLC with a short sub-2 microm column (2.1 mm x 50 mm, 1.7 microm) and a total running time of only 5h. The predicted gradient profile was further transferred to a long UHPLC column (2.1 mm x 100 mm, 1.7 microm) and a conventional HPLC columns (2.1 mm x 100 mm, 3.5 microm and 4 mm x 100 mm, 5 microm, respectively). Compared to the published methods, the newly developed dual-mode gradient is faster and more efficient at simultaneously separating hydrophilic and hydrophobic components in Danshen and its preparations.