Development of reagentless sensing system for the determination of antioxidative activity using micro-distance between the electrodes

抗氧化活性是利用食品的这一特性开发高功能食品的重要因素，测定抗氧化活性具有重要意义。本研究旨在开发一种不使用酶或特定试剂的抗氧化活性测定方法。当对水溶液中的铂等电极施加0.33 V电压时，电极上生成O_2^-，生成的O_2^-通过不比例反应生成H_2O_2。在本研究中，利用这一原理，在电极上施加负电压生成O_2^-，并通过非比例反应生成H_2O_2。当抗氧化物质存在时，该物质捕获O_2^-，并通过不成比例反应减少H_2O_2的生成。使用近端电极检测H_2O_2的量，可以研究物质的抗氧化活性和测量活性。为了有效检测O_2^-非比例反应生成的H_2O_2，在生成O_2^-的丝网印刷碳墨电极（W2）的对面放置了一个用于测量H_2O_2的丝网印刷碳墨电极（W1）。计数电极和参比电极分别采用丝网印刷碳墨和银-氯化银墨电极。为了生成O_2^-，在KCl中对W2电极施加-0.9 V。对W1电极施加1.1 V以确认该电极的传感器响应。电极间距设置为240μm。用该系统测定了儿茶素标准溶液、茶叶和蔬菜的O_2^-清除活性。茶叶和蔬菜的测定结果与DPPH法具有较好的相关性。结果表明，该系统为测定其抗氧化活性提供了一种简便、快速的方法。

Antioxidative activity is an important factor in the development of high-functional food products utilizing such characteristic of foods, and measurement of the activity is significant. This study was performed aiming at development of an antioxidative activity measurement method using no enzyme or specific reagent. When a voltage of 0.33 V is applied to an electrode such as platinum in aqueous solution, O_2^- is generated on the electrode, and the generated O_2^- produces H_2O_2 by disproportional reaction. In this study, using this principle, a negative voltage was applied to the electrode to generate O_2^-, and H_2O_2 was produced by disproportional reaction. When an antioxidative substance is present, the substance captures O_2^- and decreases the production of H_2O_2 by disproportional reaction. Detection of the amount of H_2O_2 using a proximal electrode allows investigation of antioxidative activity of substances and measurement of the activity.To effectively detect H_2O_2 produced by disproportional reaction of O_2^-, a screen-printed carbon ink electrode (W1) for measurement of H_2O_2 was placed on the opposite side of the screen-printed carbon ink electrode (W2) for generation of O_2^-. For the counter and reference electrodes, screen-printed carbon ink and silver-silver chloride ink electrode were used, respectively. To generate O_2^-, -0.9 V was applied to the W2 electrode in KCl. To the W1 electrode, 1.1 V was applied to confirm the sensor response of this electrode. The distance between the electrodes was set to 240μm. O_2^--scavenging activity of catechin standard sample solutions, tea and vegetables were measured employing this system.The results for teas and vegetables correlated satisfactorily with those obtained DPPH method. These results suggest that the proposed system provides a simple and rapid method for the determination of antioxidative activity.