Estimation of Relative Reaction Rate of Hydroxy Radical with Poly-hydroxy Benzenes: ESR Spin Trapping Combined with UV-A Photolysis

Nakagawa, Seiko

doi:10.2116/analsci.29.377

“…In the present study, we report on the development of a novel method to detect CIs from terpenes and other large alkenes in the gas phase by reaction and stabilization with spin traps, molecules widely applied for detection of free radicals in solutions with electron paramagnetic resonance, − and quantification with proton-transfer reaction mass spectrometry. The method proposed here is suitable for online quantification of CIs in the gas phase and allows for the unambiguous identification of CI-spin trap adducts in complex organic mixtures.…”

Section: Introductionmentioning

confidence: 99%

Online Quantification of Criegee Intermediates of α-Pinene Ozonolysis by Stabilization with Spin Traps and Proton-Transfer Reaction Mass Spectrometry Detection

Giorio

¹

,

Campbell

²

,

Bruschi

³

et al. 2017

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Biogenic alkenes, which are among the most abundant volatile organic compounds in the atmosphere, are readily oxidized by ozone. Characterizing the reactivity and kinetics of the first-generation products of these reactions, carbonyl oxides (often named Criegee intermediates), is essential in defining the oxidation pathways of organic compounds in the atmosphere but is highly challenging due to the short lifetime of these zwitterions. Here, we report the development of a novel online method to quantify atmospherically relevant Criegee intermediates (CIs) in the gas phase by stabilization with spin traps and analysis with proton-transfer reaction mass spectrometry. Ozonolysis of α-pinene has been chosen as a proof-of-principle model system. To determine unambiguously the structure of the spin trap adducts with α-pinene CIs, the reaction was tested in solution, and reaction products were characterized with high-resolution mass spectrometry, electron paramagnetic resonance, and nuclear magnetic resonance spectroscopy. DFT calculations show that addition of the Criegee intermediate to the DMPO spin trap, leading to the formation of a six-membered ring adduct, occurs through a very favorable pathway and that the product is significantly more stable than the reactants, supporting the experimental characterization. A flow tube set up has been used to generate spin trap adducts with α-pinene CIs in the gas phase. We demonstrate that spin trap adducts with α-pinene CIs also form in the gas phase and that they are stable enough to be detected with online mass spectrometry. This new technique offers for the first time a method to characterize highly reactive and atmospherically relevant radical intermediates in situ.

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“…Using the reaction rate constants for the target ROS vs the spin-trapping agent ( k 1 ), the concentration of the spin-trapping agent ([Spin-Trap]) and the value of IC 50 ([IC 50 ]), the reaction rate constant for the target ROS vs the scavengers ( k 2 ) can be approximated as shown in Equation 1. ( 32 ) The value of k 1 (O 2 •− vs DMPO) has been reported as 10 M −1 s −1 , ( 24 – 26 ) and the value of k 2 (O 2 •− vs nanoceria) was calculated. On the other hand, the value of k 1 ( 1 O 2 vs TPC) is unknown.…”

Section: Methodsmentioning

confidence: 99%

“…Using the reaction rate constants for the target ROS vs the spin-trapping agent (k 1 ), the concentration of the spin-trapping agent ([Spin-Trap]) and the value of IC 50 ([IC 50 ]), the reaction rate constant for the target ROS vs the scavengers (k 2 ) can be approximated as shown in Equation 1. (32) The value of k 1 (O 2…”

Section: Monitoring Of O 2 Produced By Catalase-mimic Reactionmentioning

confidence: 99%

Quenching effect of cerium oxide nanoparticles on singlet oxygen: validation of the potential for reaction with multiple reactive oxygen species

Ogawa

¹

,

Kawaguchi²,

Tanaka³

et al. 2023

J. Clin. Biochem. Nutr.

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Here we studied cerium oxide nanoparticles (nanoceria) as an agent for the future treatment of oxidative damage by validating and evaluating its scavenging activity towards reactive oxygen species (ROS) in vitro . Nanoceria has been shown to mimic the activities of superoxide dismutase and catalase, degrading superoxide (O 2 •− ) and hydrogen peroxide (H 2 O 2 ). We examined the antioxidative activity of nanoceria, focusing on its ability to quench singlet oxygen ( 1 O 2 ) in an aqueous solution. Electron paramagnetic resonance (EPR) was used to determine the rates of second-order reactions between nanoceria and three ROS ( 1 O 2 , O 2 •− , and H 2 O 2 ) in aqueous solution, and its antioxidative abilities were demonstrated. Nanoceria shows a wide range of ultraviolet-light absorption bands and thus 1 O 2 was produced directly in a nanoceria suspension using high-frequency ultrasound. The quenching or scavenging abilities of nanoceria for 1 O 2 and hypoxanthine-xanthine oxidase reaction-derived O 2 •− were examined by EPR spin-trapping methods, and the consumption of H 2 O 2 was estimated by the EPR oximetry method. Our results indicated that nanoceria interact not only with two previously reported ROS but also with 1 O 2 . Nanoceria were shown to degrade O 2 •− and H 2 O 2 , and their ability to quench 1 O 2 may be one mechanism by which they protect against oxidative damage such as inflammation.

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Irradiation of Phenolic Compounds with Ultraviolet Light Causes Release of Hydrated Electrons

Okazaki

¹

,

Takeshita

²

2018

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Estimation of Relative Reaction Rate of Hydroxy Radical with Poly-hydroxy Benzenes: ESR Spin Trapping Combined with UV-A Photolysis

Cited by 5 publications

References 15 publications

Online Quantification of Criegee Intermediates of α-Pinene Ozonolysis by Stabilization with Spin Traps and Proton-Transfer Reaction Mass Spectrometry Detection

Online Quantification of Criegee Intermediates of α-Pinene Ozonolysis by Stabilization with Spin Traps and Proton-Transfer Reaction Mass Spectrometry Detection

Quenching effect of cerium oxide nanoparticles on singlet oxygen: validation of the potential for reaction with multiple reactive oxygen species

Irradiation of Phenolic Compounds with Ultraviolet Light Causes Release of Hydrated Electrons

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