Highly defective mesoporous carbon - ionic liquid paste electrode as sensitive voltammetric sensor for determination of chlorogenic acid in herbal extracts

In this report, the preparation of a modified carbon paste electrode based on highly defective mesoporous carbon (DMC) and room temperature ionic liquid 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM.PF6) was described for sensitive voltammetric detection of chlorogenic acid (CGA) in herbal extracts. DMC with desired defective structure was synthesized via a facile method using nanosilica as a hard template, sucrose as a carbon source, and KNO3 as a defect causing agent. The characteristics of modified electrode (IL/DMC/PE) were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and chronocoulometry. The electrochemical parameters of CGA on the surface of modified electrode were determined with the results of the charge transfer coefficient (at), the number of electron transfer (n), the electrode reaction rate constant (k(s)) and saturating absorption capacity as 0.5, 2, 3.1 s(-1) and 1.42 x 10(-9) mol cm(-2) respectively. The proposed sensor exhibited a remarkably enhanced effectiveness toward the electrochemical reaction of CGA in aqueous solution. The electrocatalytic behavior was further exploited as a sensitive detection scheme for the CGA determination by Square wave voltammetry (SWV). Under optimized conditions, the linear response range and detection limit were found to be 2 x 10(-8)-2.5 x 10(-6) mol and 1 x 10(-8) mol L-1 (S/N =3) respectively. The method was successfully applied for determination of CGA in extracts of Calendula officinalis and Echinacea purpurea. (C) 2016 Elsevier B.V. All rights reserved.