A number of techniques have been used for the preparative of flavonoids. separation These include HPLC. Diaion. Amberlite NAD-2 and XAD-7, and Fractogel TSK Toyopeari Hw-40 resins. gel filtration on Sephadex, and centrifugal partition chromatography (CPC). The choice or methods and strategies varies from research group to research group and depends often on the class of flavonoid studied