Identification of flavan-3-ols and procyanidins by high-performance liquid chromatography and chemical reaction detection

A method for characterizing flavan-3-ols and procyanidins by HPLC separation in connection with on-line UV detection and chemical reaction detection (CRD) is described. The post-column derivatization of the polyphenols with 4-dimethylaminocinnamaldehyde in the presence of sulphuric acid improves the sensitivity as compared to UV detection. The extent of improvement strongly depends on the structure of the procyanidin, hence resulting in characteristic absorbance ratios (CRD/UV) for the individual compounds under given reaction conditions. The ratios are further influenced by the solvent composition, by reaction time and by temperature.