Spectrophotometric determination of hesperidin by Al(III)-hesperidin complex in water-methanol solution

The composition and the stability constant of the Al(III)-hesperidin complex were determined by suitable spectrophotometric methods and pH measurements. The formation of the complex, whose concentration stability constant log K-1 ranged from 3.46 at pH=4.0 to 4.54 at pH=5.0, was established. The conditions for the spectrophotometric determination of hesperidin, by means of the complex formation, were investigated. It was found that hesperidin can be determined in the range from 2.50x10(-5)M to 1.75x10(-4)M. The application to the determination of hesperidin in orange juice is demonstrated. All investigations were carried out with 70% methanolic solutions at room temperature (20 degrees C), constant values of pH (3.7), and ionic strength (0.01).