z Analytical Chemistry Versatile and Affordable Approach for Tracking the Oxidative Stress Caused by the Free Radicals: the Chemical Perception Dariya S. Maksym, [a] Andriy B. Zaborovsky, [a] Yuliya Y. Kubaj + , [d] Pawel Bloniarz, [b] Tomasz Pacześniak, [b] Jacques Muzart, [c] and Alexander P. Pokutsa* [a] For everybody this research may aid. Fascinating oscillations of color, kinetics of pH, cyclic voltam- metry (CV) and UV-vis spectra, ensued from supplementing of VO(acac) 2 -acetonitrile solutions with micro-amounts of H 2 O 2 , were greatly affected by the small additives of glyoxal and oxalic acid. Such effect was consisted in sufficient decreasing the sensitivity of samples by means of it pH, CV and UV-vis response onto H 2 O 2 additives. The revealed peculiarities substantiate the responsibility of free radicals (particularly * OH generated in the course of H 2 O 2 homolysis) for the discussed parameters alteration. In view of * OH are identified as most active and destructive (especially, in respect to the cellular constituents) agents can be originated in vivo, it overproduc- tion is responsible for developing of many related severe diseases. In practical aspect the undertaken research may be recommended for the oxidative stress evaluation and tracking. Introduction Oxidative stress is defined as “a state in which oxidation exceeds the antioxidant systems in the body secondary to a loss of the balance between them”. [1] Disturbances in the normal redox state of cells can cause toxic effects through the production of peroxides and free radicals that damage components of the cell, including proteins, lipids and (espe- cially) DNA. [2] Base injuring is mostly indirect and caused by reactive oxygen species (ROS), e.g. O 2  , * OOH, * OH (most destructive) and H 2 O 2 . [3] In humans, oxidative stress is thought to be responsible for developing of many severe diseases, such as ADHD, cancer, Parkinson’s, and Alzheimer’s disorder. [4] The rate of destruction is noteworthy increased by the d-block metals (e.g. Fe, Cu, V and Co). It cations participate in redox cycling and usually are represented in the human body by metaloenzymes, catalyze, among others, production of men- tioned highly active species. [5] Nowadays, to assess the oxidative stress, the set of products derived from radical-damaged cell-constituents as lipids, DNA, protein and amino acids (e.g. isoprostan, lipid peroxides, malondialdehyde, 8-hydroxyguanine, carbonyl protein) are usually used as markers. [6] Several approaches have been elaborated to reckon such oxidative derivatives. The immuno- histochemistry (IHC), HPLC, rapid ultra-high-performance liquid chromatography/mass spectrometry tandem and GC/MS-SIM techniques used to be greatly exploited. [7] However, the application of the methods enlisted above, regardless of developed achievements, still suffered by the limitations (e.g. the requirement of specialized and expensive instrumentation). Therefore, elaboration of affordable, econom- ical and simple methodologies are an actual problem. Given our previous research, we believe that pH analysis in conjunction with cyclic voltammetry (CV) and UV-vis techni- ques, are able to respond to the challenges we faced. Indeed, our studies of the impact of glyoxal (GL) and oxalic acid (OA) on VO(acac) 2 -catalyzed cyclohexane oxidation by H 2 O 2 revealed the noticeable acceleration of the process in presence of these reducing agents. Besides, the impressive abrupt decrease of pH of the VO(acac) 2 solution induced by micro-doses of H 2 O 2 was detected. Moreover, presence of OA sufficiently diminishes the sensitivity of reaction mixtures by means of it pH, cyclic voltammetry (CV) and UV-vis response to H 2 O 2 additives. [8] Hence, such features might be crucial in the matter of research. [a] D. S. Maksym, A. B. Zaborovsky, Dr. A. P. Pokutsa Department of Physical Chemistry of Fossils Fuels Institute of Physical Organic Chemistry and Chemistry of Coal NAS of Ukraine Naukova Str., 3A, Lviv 79060, Ukraine E-mail: apokutsa@ukr.net [b] Dr. P. Bloniarz, Dr. T. Pacześniak Department of Chemistry Rzeszow University of Technology P.O. Box 85, 35-959 Rzeszow, Poland [c] Dr. J. Muzart Institut de Chimie Moléculaire de Reims, UMR 6229, UFR des Sciences Exactes et Naturelles CNRS – Université de Reims Champagne-Ardenne BP 1039, 51687, Reims Cedex 2, France [d] Y. Y. Kubaj + Company «Oliyar» 81118, v. Stavchany, Lviv Region, Ukraine [ + ] This study was done while Yuliya Y. Kubaj was working at Institute [a]. Supporting information for this article is available on the WWW under https://doi.org/10.1002/slct.202003305 ChemistrySelect Full Papers doi.org/10.1002/slct.202003305 13814 ChemistrySelect 2020, 5, 13814–13818 © 2020 Wiley-VCH GmbH