Gerasimova Elena, Gazizullina Elena, Kolbaczkaya Sofya, Ivanova Alla
Analytical Chemistry Department, Institute of Chemical Engineering, Ural Federal University, 19 Mira Str., 620002 Ekaterinburg, Russia.
Antioxidants (Basel). 2022 Oct 1;11(10):1974. doi: 10.3390/antiox11101974.
For the first time, new possibilities of using the DPPH as a signal-forming oxidant molecule with potentiometric detection are shown. The CV method confirmed the presence of a quasi-reversible potential-determining system DPPH/DPPH-H under experimental conditions. This fact makes it possible to use DPPH as the model of the oxidizing agent for obtaining an analytical signal by the potentiometry method. The potentiometric approach makes it possible to obtain the value of the Nernst slope and the antioxidant capacity in one experiment. It consists of an antioxidant supplement and two consecutive DPPH supplements. In this case, the calculation of the Nernst slope is carried out by introducing the second addition of the oxidizing agent and constructing a calibration curve against the reaction background with an antioxidant. Solutions of individual antioxidants α-tocopherol, quercetin, (±)-catechin hydrate, and α-lipoic acid were studied by the developed approach. A high correlation with the results of spectrophotometric measurements is shown. At the same time, the potentiometry method is devoid of the concentration limitations of the spectrophotometric method, which was confirmed. In the study of plant materials extracts, a high correlation of antioxidant capacity, obtained by potentiometric and spectrophotometric methods, was shown only for objects whose color did not contribute to the DPPH absorption. The versatility of the potentiometric method for studying objects of any color was shown.
首次展示了使用二苯基苦味酰基自由基（DPPH）作为具有电位检测功能的信号形成氧化分子的新可能性。循环伏安法（CV）证实了在实验条件下存在准可逆的电位决定体系DPPH/DPPH-H。这一事实使得可以使用DPPH作为氧化剂模型，通过电位法获得分析信号。电位法能够在一个实验中获得能斯特斜率值和抗氧化能力。它由一种抗氧化剂补充剂和两次连续的DPPH补充剂组成。在这种情况下，能斯特斜率的计算是通过加入第二次氧化剂并构建针对含有抗氧化剂的反应背景的校准曲线来进行的。采用所开发的方法研究了单个抗氧化剂α-生育酚、槲皮素、（±）-儿茶素水合物和α-硫辛酸的溶液。结果显示与分光光度测量结果具有高度相关性。同时，电位法不存在分光光度法的浓度限制，这一点得到了证实。在对植物材料提取物的研究中，仅对于颜色不影响DPPH吸收的样品，通过电位法和分光光度法获得的抗氧化能力显示出高度相关性。展示了电位法对于研究任何颜色样品的通用性。
