Development of electrochemical sensor for detection of antioxidants using conductive ink modified screen-printed electrode

A development of ultra-high performance liquid chromatography coupled with a novel inkjet-printed conductive ink-modified electrode for a fast and simultaneous determination of polyphenolic antioxidants was achieved. Two printing techniques were chosen for fabrication and modification including (i) an in-house screen-printing method and (ii) an inkjet-printing method, respectively. A conductive ink containing graphene and polyaniline nanocomposite (G-PANI) was precisely printed onto the surface of screen-printed carbon electrode (SPCE) using a dimatix inkjet material printer. For the electrode modification, optimization of significant conditions including a G-PANI ratio and a number of inkjet-printed layers was initially investigated. Using an optimized G-PANI-modified screen-printed carbon electrode (G-PANI/SPCE) in an electrochemical batch cell, cyclic voltammetric detection of individual antioxidants was studied. Compared to a bare SPCE, the G-PANI/SPCE provided higher electrochemical sensitivity with increase (2-4 times) of peak current of each antioxidant. Moreover, four antioxidants were successfully separated and determined within 3 min using a reverse phase ultra-high performance liquid chromatography (UHPLC) with a mobile phase containing phosphate buffer (pH 3) and acetonitrile (90:10, %v/v). Under an optimal detection potential at +1.2 V vs. Ag/AgCl, linear calibrations were found to be 0.01–10 µg mL-1 with limits of detection (S/N=3) of 1.38-1.94 ng mL-1 and limit of quantitation (S/N=10) of 4.59-6.46 ng mL-1. Finally, this proposed method has been successfully used for the determination of antioxidants in tea samples. The results obtained from the presented method were highly good agreement with those obtained from a standard UHPLC-UV method.