Comparison of photometric, electrochemical and post-column fluorescence detection for the determination of flavonoids by HPLC

For the analysis of flavonoids by HPLC, we compared three different detecti on methods, namely UV, electrochemical detection and post-column chelation with aluminum followed by fluorescence detection. Ten flavonoids were used: apigenin, myricetin, luteorin, taxifolin, quercetin-3-O-sulfate, kaempfero l, isorhamnetin, isoquercitrin, quercetin and rutin. Nine flavonoids except apigenin were efficiently detected by the electrochemical method with a de tection limit of 0.025 similar to0.05 pmol. Flavonols having free 3-hydroxy l and 4-keto oxygen formed a fluorescent complex by post-column chelation a nd were detected by the fluorescence method. The detection limit of the flu orescence method was 0.05 similar to0.5 pmol. Nine flavonoids except taxifo lin were detected by the UV method (absorbance at 370 nm), but the detectio n level was poor (5 similar to 10 pmol). Flavonols added to human plasma we re recovered by solid phase extraction, and were analyzed using the three d etection methods. Most of the flavonols were efficiently detected by the el ectrochemical and fluorescence methods, and the detection limits were simil ar to those of standard samples.