Reversed-phase high-performance liquid chromatographic determination of isoflavones in plant materials after isolation by solid-phase extraction

A fast, sensitive (LODs similar to 9-17.6 nM) and precise (RSDs less than or equal to 8%) method combining solid-phase extraction (SPE) and RP-HPLC for isolation, purification as well as qualitative and quantitative determination of isoflavones (0.06-520 mu M) in plant materials is described. Plant extracts were purified and isoflavones isolated on various SPE columns. Classical sorbents were compared with new polymer sorbents as well as the wet/dry ways of extraction. Extraction efficiencies (R>90%) for determination of isoflavones (daidzein, genistein, formononetin and biochanin A) were evaluated and optimized on an Spe-ed ABN cartridge. Eluates were analyzed by RP-HPLC on C-18 bonded silica using an acetonitrile-0.1% TFA gradient and UV detection at 280 nm. The method can be used for fast determination of isoflavones in plants, foods and other biological materials. (C) 1999 Elsevier Science B.V. All rights reserved.