Fast high-performance liquid chromatography method for quality control of soy extracts

Soy extracts contain a mixture of isoflavones belonging to the group of phytoestrogens. In the quality control of soy the amount of isoflavones, both aglycones and glycosides, is usually determined by means of reversed-phase HPLC–UV. On conventional C 18-material columns, long analysis times are required in order to separate this complex mixture. In order to speed up analysis, the separation was optimized using two linked monolithic silica-based reversed-phase C 18 columns. A spectacular decrease of the analysis time, i.e. almost three-fold, was achieved by applying a flow rate of 3–4 ml/min without loosing any separation efficiency. This analysis method for determination of isoflavones in soy extracts in less than 25 min was fully validated according to the ICH guidelines.