Electroanalytical Application of Amine-grafted Attapulgite to the Sensitive Quantification of the Bioactive Compound Mangiferin

A glassy carbon electrode (GCE) coated with a thin film of organoattapulgite was used for the voltammetric detection and quantification of mangiferin (MG), a bioactive xanthone with several therapeutic properties. The used modified attapulgite was prepared by surface grafting of [3-(2-aminoethylamino)propyl]trimethoxysilane. The grafted clay was characterised by SEM, CHN elemental analysis, FTIR spectroscopy and XRD techniques. The electrochemical behaviour of MG was first investigated on bare GCE by cyclic voltammetry which showed a single irreversible oxidation peak at ca 0.770V (vs Ag/AgCl) in HCl/KCl buffer at pH1. When the GCE was covered by the organoattapulgite, the electrode response for MG increased significantly due to favourable electrostatic interactions between MG and the protonated organoclay. A sensitive voltammetric method for the determination of MG, based on adsorptive stripping voltammetry was then developed. A linear variation of MG concentration with peak current was obtained in the range from 0.61 to 10.57M, with a detection limit of 2.75x10(-7)M (S/N=3). Kinetic and chronocoulometric studies were also performed to characterise the diffusion of MG at the organoclay modified electrode. The interfering effect of some compounds likely to affect the stripping signal of MG was also evaluated, followed by the application of the developed method to a real biological sample.