EPR spectra of aerosol particles formed by pyrolysis of C3H8 plus Ar and C3H8 plus Fe(CO)5 plus Ar mixtures in a flow reactor

Paramagnetic centers in particulate formed from the oxidative pyrolysis of 1-methylnaphthalene in the presence of Fe(III)2O3 nanoparticles

“…Hence, surface-stabilized radicals were hypothesized to undergo subsequent surface-mediated, radical–radical, and/or radical–molecule, molecular growth pathways to contribute to polycyclic aromatic hydrocarbon (PAH) coalescence, soot particle inception, and soot surface growth [5]. This correlation, increased radical intensity as a function of iron concentration, has also been reported for atmospheric particulate [13] and soot generated in the presence of iron pentacarbonyl [19]. …”

“…Electron Paramagnetic Resonance (EPR) spectroscopy is the standard tool for the detection of paramagnetic species and has been widely used to elucidate the nature of combustion products produced from various sources including: propane [1], hexane [2–4], 1-methynapthalene [5], anthracene [6], diesel [4,7], jet fuel [4,8], coal [9–11], ash [12], ambient particulate [13–17], and cigarettes [18]. The EPR signal of particulate, often only a broad featureless singlet, has been proposed to be the superposition of multiple radical species based solely on the broadness of the signal and the detection of multiple radical decays [1,5,10,19]. However, the lack of hyperfine structure and broadness of the signal impedes spectral assignment and only reveals the persistent nature of radicals associated with particulate.…”

Microfluidic Electrochemical Sensor for On-Line Monitoring of Aerosol Oxidative Activity

“…1,16–18,20–22 The oldest of these assays focused on measuring redox-specific chemicals such as transition metals and polyaromatic hydrocarbons (PAH). 22 Other methods have been proposed that make use of chromatography, 18,23 electron paramagnetic resonance (EPR), 24 and fluorescence. 25,26 The dithiothreitol (DTT)-based chemical activity assay is currently the most widely reported technique used to assess the capacity of PM to catalyze ROS generation.…”

“…Various approaches for measuring the oxidative activity of PM have been developed to study PM-induced oxidative stress. − Chemical assays offer the best potential for analysis of effective ROS dose in a format that can support epidemiological research, , and many different types of chemical assays have been developed for assessing PM oxidative activity. ,− ,− The oldest of these assays focused on measuring redox-specific chemicals such as transition metals and polyaromatic hydrocarbons (PAHs) . Other methods have been proposed that make use of chromatography, , electron paramagnetic resonance (EPR), and fluorescence. , The dithiothreitol (DTT)-based chemical activity assay is currently the most widely reported technique used to assess the capacity of PM to catalyze ROS generation. , In this assay, reduced DTT is oxidized to its disulfide in the presence of ROS generated by PM. After the reaction, the remaining reduced DTT is reacted with Ellman’s reagent (5,5′-dithiobis(2-nitrobenzoic acid, DTNB) to produce a chromophore that absorbs light at 412 nm (Scheme ).…”