Total flavonoid content in plant derived beverages determined by extractive stripping voltammetry

Abstract

The catechin (CAT)-equivalent of flavonoids content of plant derived-beverages (PDBs) was estimated by partial extraction into the bare carbon paste and subsequent determination by differential pulsed voltammetry (DPV). The selectivity of the method was investigated by determining in presence of the potential interferences. While the determination of CAT in the presence of some non-flavonoid interferences was not possible by direct voltammetry, there was no interfering effect observed in the developed method. The effect of various paste compositions was studied on the extraction of the CAT onto the paste, and it was found that the combination of expanded graphite with silicon oil provides the best paste for the extraction. The RSD of 3.93% confirms a good repeatability of the developed method when 5 repetitive measurements were carried out. The LOD and LOQ of the developed method were calculated to be 1.2 × 10−8 M and 3.9 × 10−8 M, respectively. The accuracy of the developed method was controlled by analysis of the spiked sample, where the recovery rate of 98% and 104% indicate the accuracy of the developed ex-situ method. Finally, the developed method was successfully used for the determination of CAT-equivalent of flavonoids in a green tea sample.