Flavonoid content assay: influence of the reagent concentration and reaction time on the spectrophotometric behavior of the aluminium chloride--flavonoid complex.

The spectrophotometric assay based on aluminum chloride complex formation is one of the most commonly analytical procedures applied to flavonoid content determination. However, only a few optimization studies on the reaction conditions were done so far. The present work aims to the investigation of aluminum chloride concentration and reaction time effects on the spectrophotometric behavior of different flavonoids. The effects of both variation factors were studied by Central Composite Design and Response Surface Analysis methodology. The absorption data analysis showed that the effects of reaction time and reagent concentration on the absorption maximum are intricate and specific. A clear relationship between spectrophotometric behavior and flavonoid type or particular structure patterns could not be established.