Electrochemical Sensor for Detection of Polyphenols in Tea and Wine with Differential Pulse Voltammetry and Electrochemical Impedance Spectroscopy Utilizing Tyrosinase and Gold Nanoparticles Decorated Biomembrane

Abstract

This paper reports a biocompatible sensor based on gold nanoparticles (AuNPs) and enzyme tyrosinase (Tyr) modified egg shell membrane (ESM) on glassy carbon electrode (GCE) as an effective analytical tool for the detection of polyphenols. AuNPs were synthesized on the membrane from gold chloride solution (HAuCl4) without the application of toxic reducing agent. The sensor exhibited excellent linear relationship (r > 0.99) with micromolar concentrations of analyte and high sensitivity in differential pulse voltammetry for gallic acid (GA), caffeic acid (CA) and catechin hydrate (CH). The detection limits were found to be 1.707 μM, 0.752 μM and 0.714 μM for GA, CA and CH respectively (S/N = 3) at three different anodic potentials vs Ag/AgCl reference electrode (pH 6). Results showed good sensor reusability without loss of sensitivity. Modified membrane without AuNPs was also analyzed to detect polyphenol content by simple colorimetry. The modified sensor was characterized by electrochemical impedance spectroscopy (EIS). The developed sensor was successfully employed for detection of polyphenol content in commercially available tea and wine samples and results compared to traditional methods e.g. HPLC. The sensitivity values (193.9, 82 and 73.4 nA μM−1 cm−2 for CH, GA and CA) were high enough making the method a promising tool for practical gradation of real samples.