FLUORESCENCE DETECTION OF FLAVONOLS IN HPLC BY POSTCOLUMN CHELATION WITH ALUMINUM

Flavonols are dietary antioxidants which may prevent coronary heart di sease, To be able to study absorption of flavonols in humans, we devel oped a postcolumn derivatization with aluminum for HPLC with fluoresce nce detection, Variables governing postcolumn chelation, such as water content, buffer, organic modifier of the eluent, concentration of Al3 +, presence of acetic acid in the postcolumn reagent, and temperature, were studied and optimized. Of the flavonoids, only flavonols that co ntain a free 3-hydroxyl and 4-keto oxygen binding site form fluorescen t complexes with Al3+, The method has a detection limit of 0.15 ng/mL for quercetin, 0.05 ng/mL for kaempferol, 0.45 ng/mL for myricetin, an d 0.05 mg/mL for isorhamnetin, thus improving detectability of quercet in 300-fold as compared to that possible with UV detection, The reprod ucibility relative standard deviation of the method is 1.4%. This extr emely sensitive method enables, for the first time, determination of f lavonols in body fluids after consumption of a normal diet.