Voltammetric determination of polyphenolic content as rosmarinic acid equivalent in tea samples using pencil graphite electrodes

The quasi-reversible, diffusion controlled behavior of rosmarinic acid (RA) on a disposable pencil graphite electrode (PGE) was established by cyclic voltammetry. Using the anodic oxidation peak presented by RA on the PGE a differential pulse voltammetric (DPV) method was developed for the quantitative determination of RA. The linear range was 10 −8 – 10 −5 M RA and the detection and quantification limits were 7.93 × 10 −9 M and 2.64 × 10 −8 M RA, respectively. The applicability of the developed method was tested by recovery studies and by the assessment of the total polyphenolic contents (TPC DPV ) of green, white and black Turkish teas, which were found to be 40.74, 30.04 and 23.97 mg rosmarinic acid equivalent/g dry tea, respectively. These results were in good agreement with those obtained by the Folin-Ciocalteu method. The developed method is a sensitive and cheap tool for the rapid and precise evaluation of TPC DPV of tea samples.