Ultra-high performance liquid chromatographic determination of antioxidants in teas using inkjet-printed graphene–polyaniline electrode

• Inkjet-printed G–PANI/SPCE coupled with UHPLC was successfully developed.
• G–PANI enhanced electrochemical detection of antioxidants after their separation.
• Antioxidants in teas were successfully separated and determined within 3 min.

A development of ultra-high performance liquid chromatographic 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 selected 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 casted onto the surface of screen-printed carbon electrode (SPCE) using a dimatix inkjet material printer. Compared to a bare SPCE, the G–PANI-modified screen-printed carbon electrode (G–PANI/SPCE) exhibited 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 and acetonitrile (90:10 v/v). Under an optimal detection potential at +1.2 V vs. Ag/AgCl, linear calibrations and limits of detection (S/N=3) for antioxidants were found to be 0.01–10 µg mL−1 and 1.38–1.94 ng mL−1, respectively. Finally, this proposed method has been successfully used for the determination of antioxidants in tea samples, the results obtained from our presented method were within a highly good agreement those obtained from a standard UHPLC–UV method.

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