Spectrofluorimetric determination of quercetin in pharmaceutical dosage forms

Abstract

A simple, accurate and precise method based on the fluorescence properties of the aluminum(III)-quercetin complex, for the determination of quercetin, has been developed and validated. The complex has strong emission at pH 3.30, lambda(em) = 480 nm, with lambda(ex) = 420 nm. The linearity range of quercetin determination was 1.5-60.5 ng ml(-1) with LOD 0.09 ng ml(-1) and LOQ 0.27 ng ml(-1). Recovery values in the range of 99.9-100.2% indicate a good accuracy of the method. The established method was applied for the determination of quercetin in capsules, with a recovery value of 98.3%, standard deviation of 0.22% and coefficient of variation of 0.09%. The reliability of the method was checked by the newly developed RP-HPLC/UV method for capsules with the direct determination of quercetin after separation. The good agreement between the two methods indicates the applicability of the proposed spectrofluorimetric method for quercetin determination in pharmaceutical dosage forms, with high reproducibility, and enables the direct and simple determination without its prior extraction from samples. The proposed spectrofluorimetric method has much better sensitivity and LOD and LOQ values that are about 1000 times lower than data reported in the literature.