An improved method for determination of isoflavones in soybean powder by liquid chromatography

Several extraction and separation methods were evaluated and then developed for determination of isoflavone in soybean powder Results showed that the highest yield of isoflavones was achieved by using defatted soybean powder as raw material, followed by shaking extraction for 2 h with a mixture of acetone and 0.1 M hydrochloric acid as solvent. A mobile phase of acetonitrile (A) and water (B) with the following gradient elution was developed: 5% A in B initially, then increased to 10% A in 5 min, 25% A in 15 min, 32% A in 22 min and returned to 5% A in 27 min. Twelve isoflavones in soybean powder were resolved within 20 min using a Vydac 201TP54 column flow rate 2.0 mL min(-1) and detection at 262 nm. The amounts of various isoflavones in soybean powder were also determined.