Spectrophotometric Determination of Total Flavonoids in Edible Vegetable Oil

A saponification-color reaction-spectrophotometric method for determination of total flavonoids in edible vegetable oil samples was established. The edible oil sample was saponified with potassium hydroxide ethanol solution under the condition of 80℃water bath and then directly colored with NaNO₂-Al(NO₃)₃ solution. The wavelength of 353 nm was selected to determine absorbance. The standard solution was prepared using rutin as the standard sample and the decolorized edible oil sample as solvent which the concentration had been determined, and the standard curve was measured after color reaction. The results showed that the relative standard deviation (RSD) of soybean oil samples was 0.82% in the day and 1.8% day to day. The antioxidant, sterol and polyphenol in edible oil have been tested with no interference on the determination. The method recovery was determined as 99.1%±0.7%. The total flavonoids contents were analyzed as 10.1 mg/L in a soybean oil sample and 13.1 mg/L in a corn oil sample respectively. The method avoids the emulsification phenomenon in the experiment by saponifying the sample, which is easy operation and generates well precision. It can be applied to determine total flavones in vegetable oil.