Polyethylenimine-Based Electrochemical Sensor for the Determination of Caffeic Acid in Aromatic Herbs

Abstract

An electrochemical sensor based on carbon paste modified with polyethyleneimine was developed and employed for the determination of caffeic acid in aromatic herbs. The sensor was prepared by mixing polyethylenimine (1.5% v/v), graphite powder, and mineral oil. The polyethylenimine-based electrode showed an enhancement of charge transfer at the electrode–solution interface and a higher current intensity for the electrochemical reaction of caffeic acid, in comparison to the unmodified electrode. The calibration plot of caffeic acid constructed in 0.1 mol L−1 acetate buffer (pH 5.0) by square wave voltammetry was linear in the range of 1.25 to 19.9 μmol L−1 with a limit of detection of 0.13 μmol L−1, respectively. Finally, the proposed sensor was employed to monitor the caffeic acid with accuracy in dried Thymus vulgaris and Salvia officinalis samples, with recovery results from 93 to 105%.