Department of Chemistry, Faculty of Engineering, Istanbul University, Avcilar 34320, Istanbul, Turkey.
Anal Chem. 2010 May 15;82(10):4252-8. doi: 10.1021/ac100646k.
A low-cost optical sensor using an immobilized chromogenic redox reagent was devised for measuring the total antioxidant level in a liquid sample without requiring sample pretreatment. The reagent, copper(II)-neocuproine (Cu(II)-Nc) complex, was immobilized onto a cation-exchanger film of Nafion, and the absorbance changes associated with the formation of the highly colored Cu(I)-Nc chelate as a result of reaction with antioxidants was measured at 450 nm. The sensor gave a linear response over a wide concentration range of standard antioxidant compounds. The trolox equivalent antioxidant capacity (TEAC) values of various antioxidants reported in this work using the optical sensor-based "cupric reducing antioxidant capacity" (CUPRAC) assay were comparable to those of the standard solution-based CUPRAC assay, showing that the immobilized Cu(II)-Nc reagent retained its reactivity toward antioxidants. Common food ingredients like oxalate, citrate, fruit acids, and reducing sugars did not interfere with the proposed sensing method. This assay was validated through linearity, additivity, precision, and recovery, demonstrating that the assay is reliable and robust. The developed optical sensor was used to screen total antioxidant capacity (TAC) of some commercial fruit juices without preliminary treatment and showed a promising potential for the preparation of antioxidant inventories of a wide range of food plants.
一种使用固定化显色氧化还原试剂的低成本光学传感器被设计用于测量液体样品中的总抗氧化水平，而无需样品预处理。该试剂为铜（II）-邻菲啰啉（Cu（II）-Nc）配合物，固定在 Nafion 的阳离子交换剂膜上，并通过与抗氧化剂反应形成高度显色的 Cu（I）-Nc 螯合物来测量 450nm 处的吸光度变化。该传感器在标准抗氧化化合物的宽浓度范围内给出了线性响应。本工作使用基于光学传感器的“铜还原抗氧化能力”（CUPRAC）测定法测定的各种抗氧化剂的 Trolox 等效抗氧化能力（TEAC）值与基于标准溶液的 CUPRAC 测定法相当，表明固定化的 Cu（II）-Nc 试剂保持了其对抗氧化剂的反应性。像草酸盐、柠檬酸盐、水果酸和还原糖这样的常见食物成分不会干扰所提出的传感方法。该测定法通过线性、加性、精密度和回收率进行了验证，表明该测定法可靠且稳健。所开发的光学传感器用于筛选一些商业果汁的总抗氧化能力（TAC）而无需预处理，并显示出对广泛的植物性食物的抗氧化剂含量进行制备的有希望的潜力。
