Rapid determination of total polyphenolic content in tea samples based on caffeic acid voltammetric behaviour on a disposable graphite electrode

Abstract

The present paper describes the voltammetric behaviour and the quantitative determination of caffeic acid (CA) on a disposable pencil graphite electrode (PGE). The anodic peak current of CA recorded by differential pulse voltammetry (DPV) varies linearly with CA concentration in the range 1×10−7–3×10−3M. The detection and quantification limits were 8.83×10−8M and 2.94×10−7M caffeic acid, respectively. The mean recoveries of CA from Turkish green, white and black teas were 98.30%, 99.57% and 91.46%. For these three tea types the corresponding total polyphenolic contents (TPCs) evaluated by DPV on PGE were 35.81, 34.59 and 31.21mg caffeic acid equivalent/g tea, respectively. These TPC values were in good accordance with those obtained by the Folin–Ciocalteu method. The developed DPV on PGE method constitutes a simple and inexpensive tool for the rapid assessment of TPC of tea samples.