Chemical Detection of Short-Lived Species Induced in Aqueous Media by Atmospheric Pressure Plasma

Abstract

Non-thermal atmospheric pressure plasmas are widely used in biomedical research and clinical applications. Such plasmas generate a variety of reactive oxygen and nitrogen species upon interaction with ambient surroundings. These species further interact with a biological substrate and are responsible for the biomedical effects of plasma. Liquid water is an essential part of any biological systems. Some of the most reactive species induced by plasma in aqueous media are radicals and atoms. Hence, the presence of certain chemical components in a plasma 'cocktail' presents an important task for both understanding and further development of plasma systems with specific purposes. In this chapter, we discuss various methods of detection of the plasma-generated short-lived reactive species. We dissert various plasma-induced radicals and atoms (•OH, O 2 • − /•OOH, •NO, O), together with non-radical short-lived species (− OONO, O 3 , 1 O 2). Electron paramagnetic resonance (EPR) is the most direct method of radical detection in water-based media. Special attention is paid to the limitations of the detection methods, with an emphasis on spin trapping used in EPR analysis.

Plasma‐activated water: Physicochemical properties, microbial inactivation mechanisms, factors influencing antimicrobial effectiveness, and applications in the food industry

“…Several techniques have been used currently to identify and quantify the reactive species generated in plasma-treated liquids, including electron paramagnetic resonance (EPR), UV-vis spectrophotometry, chemical dosimetry, liquid chromatography in addition to colorimetric and fluorescence method (Griess reagent, nitrate assay kit, titanium (IV) oxysulfate, amplex red hydrogen peroxide [H 2 O 2 ] assay kit) (Hoeben et al, 2019;Jo, Joh, Chung, & Chung, 2020;Kučerová, Machala, & Hensel, 2020;Pandiyaraj et al, 2020;Xu et al, 2020). While laser-induced fluorescence (LIF), Fourier-transform infrared (FTIR) spectroscopy, mass-spectrometry, and gas sensors or analyzers are used for product detection in the gas phase (Gorbanev & Bogaerts, 2018;Khlyustova et al, 2019). When PAW is generated, different processes occur at the interface layer, such as the transfer of gaseous species into the liquid, and chemical reactions between gaseous species and liquid molecules (Wende, von Woedtke, Weltmann, & Bekeschus, 2018).…”

“…In recent years, PAW has also been confirmed to possess outstanding biological activity in biomedical and agricultural sectors (Kaushik et al., 2018; Sajib et al., 2020). During PAW generation, the energetic particles in the plasma phase are trapped in the aqueous liquids, and a series of reactions at the gas–liquid interface is initiated, leading to various primary and secondary reactive species dissolving in the liquid (Gorbanev & Bogaerts, 2018; Khlyustova, Labay, Machala, Ginebra, & Canal, 2019). These reactive species, including reactive oxygen species (ROS) and reactive nitrogen species (RNS) are responsible for the chemical and biological effects of PAW.…”

Quantification of Plasma-Produced Hydroxyl Radicals in Solution and their Dependence on the pH

“…The main methods involve the use of chemical probes that react selectively with the HO radicals to give relatively stable adducts/products that can be detected spectroscopically (by electron paramagnetic resonance if they have unpaired electrons or by fluorimetry if they are fluorescent). 8 The methods for the quantification of RS differ whether they are short or long-lived; contrary to what occurs for long-lived species, the concentration of HO radicals and other short-lived RS (like superoxide, peroxonitrite, singlet oxygen, etc.) cannot be quantified by simply multiplying their formation rate by the treatment time because, due to their high reactivity, they are not stable and thus do not accumulate in solution.…”

“…The wide variety of applications that cold atmospheric plasmas (CAPs) reached in the last decades, ranging from gas conversion to agriculture and from the environment to manufacturing and medicine, − is mostly due to the fine tunability of the nature and amount of reactive species (RS) that are produced by a CAP in a gas or in a liquid. This has been possible thanks to the correlation of the RS production with the CAP parameters and to the methods and protocols that have been developed and adapted to detect and quantify plasma-produced RS. − The majority of them are focused on the long-lived species, like O 3 , H 2 O 2 , H 3 O + , NO 2 – , and NO 3 – , because their reactivity can be more easily controlled and their quantification can be done after the treatment, without interference from the plasma. ,− Nevertheless, analysis of short-lived RS (especially HO • , O 2 – • , HOO • , and OONO – ) is of paramount importance because they are primarily responsible for the biological action during direct CAP treatments and are the source of the long-lived ones …”

Reactive Oxygen Species Generated by Cold Atmospheric Plasmas in Aqueous Solution: Successful Electrochemical Monitoring in Situ under a High Voltage System

“…Several methods are described for the detection of reactive oxygen and nitrogen species in solution and most of them are based on an indirect detection by using different probes such as spin traps, fluorescent, colorimetric, or biological probes . These methods have, however, some limitations (semiquantitative results, autodegradation of spin-adducts, damage of biological probes, nonselectivity), , which is problematic considering the wide variety of RONS produced by CAPs. Thus, even if these methods give a good assessment of RONS generation in liquids treated by plasmas, it is highly desired in the community to have more information about their nature and fate after production.…”