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.本研究开发了一种结合新型喷墨打印导电改性电极的超高效液相色谱（Ultra-High Performance Liquid Chromatography, UHPLC）方法，用于快速同时测定多酚类抗氧化剂。本研究选用两种印刷技术分别用于电极的制备与改性：(i) 自主研发的丝网印刷法，(ii) 喷墨印刷法。采用迪迈泰克（Dimatix）喷墨材料打印机，将包含石墨烯与聚苯胺纳米复合物（G-PANI）的导电油墨精准打印至丝网印刷碳电极（Screen-Printed Carbon Electrode, SPCE）表面。针对电极改性过程，本研究首先对关键条件进行了优化，包括G-PANI油墨配比与喷墨打印层数。将优化后的G-PANI改性丝网印刷碳电极（G-PANI/SPCE）置于电化学池体系中，开展了单一抗氧化剂的循环伏安检测研究。与裸丝网印刷碳电极（bare SPCE）相比，G-PANI/SPCE的电化学灵敏度显著提升，各抗氧化剂的峰电流提升2~4倍。此外，采用流动相为pH 3磷酸盐缓冲液与乙腈体积比90:10的反相超高效液相色谱法，可在3分钟内完成四种抗氧化剂的有效分离与定量检测。在+1.2 V（vs. Ag/AgCl）的最优检测电位下，该方法的线性范围为0.01~10 μg·mL⁻¹，信噪比（S/N=3）下的检出限（Limit of Detection, LOD）为1.38~1.94 ng·mL⁻¹，信噪比（S/N=10）下的定量限（Limit of Quantitation, LOQ）为4.59~6.46 ng·mL⁻¹。最后，本研究将所提出的方法成功应用于茶叶样品中抗氧化剂的定量检测，所得结果与标准超高效液相色谱-紫外检测法（UHPLC-UV）的测定结果具有高度一致性。