title: Fluorescence detection of flavonols in HPLC by postcolumn chelation with aluminum.
abstract: Flavonols are dietary antioxidants which may prevent coronary heart disease. To be able to study absorption of flavonols in humans, we developed a postcolumn derivatization with aluminum for HPLC with fluorescence detection. Variables governing postcolumn chelation, such as water content, buffer, organic modifier of the eluent, concentration of Al(3+), presence of acetic acid in the postcolumn reagent, and temperature, were studied and optimized. Of the flavonoids, only flavonols that contain a free 3-hydroxyl and 4-keto oxygen binding site form fluorescent complexes with Al(3+). 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, and 0.05 mg/mL for isorhamnetin, thus improving detectability of quercetin 300-fold as compared to that possible with UV detection. The reproducibility relative standard deviation of the method is 1.4%. This extremely sensitive method enables, for the first time, determination of flavonols in body fluids after consumption of a normal diet.
authors: DLO [Formula: see text] State Institute for Quality Control of Agricultural Products (RIKILT-DLO), Bornsesteeg 45, 6708 PD Wageningen, The Netherlands.
authors: P C
authors: PC
authors: Hollman
authors: J M
authors: JM
authors: van Trijp
authors: M N
authors: MN
authors: Buysman