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Khachatryan L, Rezk MY, Nde D, Hasan F, Lomnicki S, Boldor D, Cook R, Sprunger P, Hall R, Cormier S. New Features of Laboratory-Generated EPFRs from 1,2-Dichlorobenzene (DCB) and 2-Monochlorophenol (MCP). ACS Omega 2024; 9:9226-9235. [PMID: 38434874 PMCID: PMC10905596 DOI: 10.1021/acsomega.3c08271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 12/18/2023] [Accepted: 01/22/2024] [Indexed: 03/05/2024]
Abstract
The present research is primarily focused on investigating the characteristics of environmentally persistent free radicals (EPFRs) generated from commonly recognized aromatic precursors, namely, 1,2-dichlorobenzene (DCB) and 2-monochlorophenol (MCP), within controlled laboratory conditions at a temperature of 230 °C, termed as DCB230 and MCP230 EPFRs, respectively. An intriguing observation has emerged during the creation of EPFRs from MCP and DCB utilizing a catalyst 5% CuO/SiO2, which was prepared through various methods. A previously proposed mechanism, advanced by Dellinger and colleagues (a conventional model), postulated a positive correlation between the degree of hydroxylation on the catalyst's surface (higher hydroxylated, HH and less hydroxylated, LH) and the anticipated EPFR yields. In the present study, this correlation was specifically confirmed for the DCB precursor. Particularly, it was observed that increasing the degree of hydroxylation at the catalyst's surface resulted in a greater yield of EPFRs for DCB230. The unexpected finding was the indifferent behavior of MCP230 EPFRs to the surface morphology of the catalyst, i.e., no matter whether copper oxide nanoparticles are distributed densely, sparsely, or completely agglomerated. The yields of MCP230 EPFRs remained consistent regardless of the catalyst type or preparation protocol. Although current experimental results confirm the early model for the generation of DCB EPFRs (i.e., the higher the hydroxylation is, the higher the yield of EPFRs), it is of utmost importance to closely explore the heterogeneous alternative mechanism(s) responsible for generating MCP230 EPFRs, which may run parallel to the conventional model. In this study, detailed spectral analysis was conducted using the EPR technique to examine the nature of DCB230 EPFRs and the aging phenomenon of DCB230 EPFRs while they exist as surface-bound o-semiquinone radicals (o-SQ) on copper sites. Various aspects concerning bound radicals were explored, including the hydrogen-bonding tendencies of o-semiquinone (o-SQ) radicals, the potential reversibility of hydroxylation processes occurring on the catalyst's surface, and the analysis of selected EPR spectra using EasySpin MATLAB. Furthermore, alternative routes for EPFR generation were thoroughly discussed and compared with the conventional model.
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Affiliation(s)
- Lavrent Khachatryan
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Marwan Y. Rezk
- Department
of Engineering Science, Biological Engineering, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Divine Nde
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Farhana Hasan
- Department
of Environmental Sciences, Louisiana State
University, Baton
Rouge, Louisiana 70803, United States
| | - Slawomir Lomnicki
- Department
of Environmental Sciences, Louisiana State
University, Baton
Rouge, Louisiana 70803, United States
| | - Dorin Boldor
- Department
of Engineering Science, Biological Engineering, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Robert Cook
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Phillip Sprunger
- Department
of Physics and Astronomy, Louisiana State
University, Baton
Rouge, Louisiana 70803, United States
| | - Randall Hall
- Natural
Sciences and Mathematics, School of Health and Natural Sciences, Dominican University of California, San Rafael, California 94901, United States
| | - Stephania Cormier
- Department
of Biological Sciences, LSU Superfund Research
Program and Pennington Biomedical Research Center, Baton Rouge, Louisiana 70808, United States
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Aryal A, Noël A, Khachatryan L, Cormier SA, Chowdhury PH, Penn A, Dugas TR, Harmon AC. Environmentally persistent free radicals: Methods for combustion generation, whole-body inhalation and assessing cardiopulmonary consequences. Environ Pollut 2023; 334:122183. [PMID: 37442324 PMCID: PMC10528481 DOI: 10.1016/j.envpol.2023.122183] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 07/04/2023] [Accepted: 07/10/2023] [Indexed: 07/15/2023]
Abstract
Particulate matter (PM) containing environmentally persistent free radicals (EPFRs) results from the incomplete combustion of organic wastes which chemisorb to transition metals. This process generates a particle-pollutant complex that continuously redox cycles to produce reactive oxygen species. EPFRs are well characterized, but their cardiopulmonary effects remain unknown. This publication provides a detailed approach to evaluating these effects and demonstrates the impact that EPFRs have on the lungs and vasculature. Combustion-derived EPFRs were generated (EPFR lo: 2.1e-16 radical/g, EPFR hi: 5.5e-17 radical/g), characterized, and verified as representative of those found in urban areas. Dry particle aerosolization and whole-body inhalation were established for rodent exposures. To verify that these particles and exposures recapitulate findings relevant to known PM-induced cardiopulmonary effects, male C57BL6 mice were exposed to filtered air, ∼280 μg/m3 EPFR lo or EPFR hi for 4 h/d for 5 consecutive days. Compared to filtered air, pulmonary resistance was increased in mice exposed to EPFR hi. Mice exposed to EPFR hi also exhibited increased plasma endothelin-1 (44.6 vs 30.6 pg/mL) and reduced nitric oxide (137 nM vs 236 nM), suggesting vascular dysfunction. Assessment of vascular response demonstrated an impairment in endothelium-dependent vasorelaxation, with maximum relaxation decreased from 80% to 62% in filtered air vs EPFR hi exposed mice. Gene expression analysis highlighted fold changes in aryl hydrocarbon receptor (AhR) and antioxidant response genes including increases in lung Cyp1a1 (8.7 fold), Cyp1b1 (9 fold), Aldh3a1 (1.7 fold) and Nqo1 (2.4 fold) and Gclc (1.3 fold), and in aortic Cyp1a1 (5.3 fold) in mice exposed to EPFR hi vs filtered air. We then determined that lung AT2 cells were the predominate locus for AhR activation. Together, these data suggest the lung and vasculature as particular targets for the health impacts of EPFRs and demonstrate the importance of additional studies investigating the cardiopulmonary effects of EPFRs.
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Affiliation(s)
- Ankit Aryal
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana, 70803, USA
| | - Alexandra Noël
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana, 70803, USA
| | - Lavrent Khachatryan
- Department of Chemistry, Louisiana State University A&M College, Baton Rouge, Louisiana, 70803, USA
| | - Stephania A Cormier
- Department of Biological Sciences, Louisiana State University A&M College and the Pennington Biomedical Research Institute, Baton Rouge, Louisiana, 70803, USA
| | - Pratiti H Chowdhury
- Department of Biological Sciences, Louisiana State University A&M College and the Pennington Biomedical Research Institute, Baton Rouge, Louisiana, 70803, USA
| | - Arthur Penn
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana, 70803, USA
| | - Tammy R Dugas
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana, 70803, USA
| | - Ashlyn C Harmon
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana, 70803, USA.
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Yamamoto A, Sly PD, Chew KY, Khachatryan L, Begum N, Yeo AJ, Vu LD, Short KR, Cormier SA, Fantino E. Environmentally persistent free radicals enhance SARS-CoV-2 replication in respiratory epithelium. Exp Biol Med (Maywood) 2023; 248:271-279. [PMID: 36628928 PMCID: PMC9836833 DOI: 10.1177/15353702221142616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 10/28/2022] [Indexed: 01/12/2023] Open
Abstract
Epidemiological evidence links lower air quality with increased incidence and severity of COVID-19; however, mechanistic data have yet to be published. We hypothesized air pollution-induced oxidative stress in the nasal epithelium increased viral replication and inflammation. Nasal epithelial cells (NECs), collected from healthy adults, were grown into a fully differentiated epithelium. NECs were infected with the ancestral strain of SARS-CoV-2. An oxidant combustion by-product found in air pollution, the environmentally persistent free radical (EPFR) DCB230, was used to mimic pollution exposure four hours prior to infection. Some wells were pretreated with antioxidant, astaxanthin, for 24 hours prior to EPFR-DCB230 exposure and/or SARS-CoV-2 infection. Outcomes included viral replication, epithelial integrity, surface receptor expression (ACE2, TMPRSS2), cytokine mRNA expression (TNF-α, IFN-β), intracellular signaling pathways, and oxidative defense enzymes. SARS-CoV-2 infection induced a mild phenotype in NECs, with some cell death, upregulation of the antiviral cytokine IFN-β, but had little effect on intracellular pathways or oxidative defense enzymes. Prior exposure to EPFR-DCB230 increased SARS-CoV-2 replication, upregulated TMPRSS2 expression, increased secretion of the proinflammatory cytokine TNF-α, inhibited expression of the mucus producing MUC5AC gene, upregulated expression of p21 (apoptosis pathway), PINK1 (mitophagy pathway), and reduced levels of antioxidant enzymes. Pretreatment with astaxanthin reduced SARS-CoV-2 replication, downregulated ACE2 expression, and prevented most, but not all EPFR-DCB230 effects. Our data suggest that oxidant damage to the respiratory epithelium may underly the link between poor air quality and increased COVID-19. The apparent protection by antioxidants warrants further research.
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Affiliation(s)
- Ayaho Yamamoto
- Child Health Research Centre, The
University of Queensland, South Brisbane, QLD 4101, Australia
| | - Peter D Sly
- Child Health Research Centre, The
University of Queensland, South Brisbane, QLD 4101, Australia
| | - Keng Yih Chew
- School of Chemistry and Molecular
Biosciences, The University of Queensland, St Lucia, QLD 4067, Australia
| | - Lavrent Khachatryan
- Department of Chemistry, Louisiana
State University, Baton Rouge, LA 70803, USA
| | - Nelufa Begum
- Child Health Research Centre, The
University of Queensland, South Brisbane, QLD 4101, Australia
| | - Abrey J Yeo
- Child Health Research Centre, The
University of Queensland, South Brisbane, QLD 4101, Australia
- Centre for Clinical Research, The
University of Queensland, Herston, QLD 4006, Australia
| | - Luan D Vu
- Department of Biological Sciences, and
Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA
70803, USA
| | - Kirsty R Short
- School of Chemistry and Molecular
Biosciences, The University of Queensland, St Lucia, QLD 4067, Australia
| | - Stephania A Cormier
- Department of Biological Sciences, and
Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA
70803, USA
| | - Emmanuelle Fantino
- Child Health Research Centre, The
University of Queensland, South Brisbane, QLD 4101, Australia
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Bei J, Xu X, Zhan M, Li X, Jiao W, Khachatryan L, Wu A. Revealing the Mechanism of Dioxin Formation from Municipal Solid Waste Gasification in a Reducing Atmosphere. Environ Sci Technol 2022; 56:14539-14549. [PMID: 36164751 DOI: 10.1021/acs.est.2c05830] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Gasification is an effective technology for the thermal disposal of municipal solid waste (MSW) with lower dioxin emission compared to the prevailing incineration process. Nevertheless, the mechanism of dioxin formation in the reducing atmosphere during the gasification process was seldomly explored. Herein, the effects of the atmosphere, temperature, and chlorine source were systematically investigated in terms of dioxin distribution. With CO2 and H2O as gasification agents, a reducing reaction atmosphere was formed with abundant H2 which effectively suppressed the generation of C-Cl, contributing to a substantial decrease of dioxin concentration by ∼80% compared to the incineration process. The formation of dioxin was favored at temperatures below 700 °C with its peak concentration achieved at 500 °C. It was unveiled that inorganic chlorine played a dominant role in the reducing atmosphere, with a lower proportion of C-O-C/O-C═O on residual slag compared to an oxidizing atmosphere. Additionally, the generated H2 reduced the concentration of dioxins by attacking C-Cl and inhibiting the crucial Deacon reaction for dioxin formation, validated by density functional theory calculation. Eventually, the formation route paradigm and the reaction mechanism of dioxin formation from MSW gasification were revealed, facilitating and rationally guiding the control of dioxin emission.
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Affiliation(s)
- Jianye Bei
- College of Metrology and Measurement Engineering, China Jiliang University, Hangzhou 310018, Zhejiang, China
- State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China
| | - Xu Xu
- College of Metrology and Measurement Engineering, China Jiliang University, Hangzhou 310018, Zhejiang, China
| | - Mingxiu Zhan
- College of Metrology and Measurement Engineering, China Jiliang University, Hangzhou 310018, Zhejiang, China
- State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, China, 18 Shuangqing Road, Haidian District, Beijing 100085, PR China
| | - Xiaodong Li
- State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China
| | - Wentao Jiao
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, China, 18 Shuangqing Road, Haidian District, Beijing 100085, PR China
| | - Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Angjian Wu
- State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China
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Khachatryan L, Barekati-Goudarzi M, Asatryan R, Ozarowski A, Boldor D, Lomnicki SM, Cormier SA. Metal-Free Biomass-Derived Environmentally Persistent Free Radicals (Bio-EPFRs) from Lignin Pyrolysis. ACS Omega 2022; 7:30241-30249. [PMID: 36061701 PMCID: PMC9434622 DOI: 10.1021/acsomega.2c03381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 08/04/2022] [Indexed: 06/15/2023]
Abstract
To assess contribution of the radicals formed from biomass burning, our recent findings toward the formation of resonantly stabilized persistent radicals from hydrolytic lignin pyrolysis in a metal-free environment are presented in detail. Such radicals have particularly been identified during fast pyrolysis of lignin dispersed into the gas phase in a flow reactor. The trapped radicals were analyzed by X-band electron paramagnetic resonance (EPR) and high-frequency (HF) EPR spectroscopy. To conceptualize available data, the metal-free biogenic bulky stable radicals with extended conjugated backbones are suggested to categorize as a new type of metal-free environmentally persistent free radicals (EPFRs) (bio-EPFRs). They can be originated not only from lignin/biomass pyrolysis but also during various thermal processes in combustion reactors and media, including tobacco smoke, anthropogenic sources and wildfires (forest/bushfires), and so on. The persistency of bio-EPFRs from lignin gas-phase pyrolysis was outlined with the evaluated lifetime of two groups of radicals being 33 and 143 h, respectively. The experimental results from pyrolysis of coniferyl alcohol as a model compound of lignin in the same fast flow reactor, along with our detailed potential energy surface analyses using high-level DFT and ab initio methods toward decomposition of a few other model compounds reported earlier, provide a mechanistic view on the formation of C- and O-centered radicals during lignin gas-phase pyrolysis. The preliminary measurements using HF-EPR spectroscopy also support the existence of O-centered radicals in the radical mixtures from pyrolysis of lignin possessing a high g value (2.0048).
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Affiliation(s)
- Lavrent Khachatryan
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | | | - Rubik Asatryan
- Department
of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Andrew Ozarowski
- National
High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Florida, Tallahassee 32310, United States
| | - Dorin Boldor
- Department
of Biological and Agricultural Engineering, LSU AgCenter and LSU A&M College, Baton Rouge, Louisiana 70803, United States
| | - Slawomir M. Lomnicki
- Department
of Environmental Sciences, Louisiana State
University, Baton Rouge, Louisiana 70803, United States
| | - Stephania A. Cormier
- Department
of Biological Sciences, LSU Superfund Research
Program and Pennington Biomedical Research Center, Baton Rouge, Louisiana 70808, United States
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6
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Mărculescu C, Tîrţea RN, Khachatryan L, Boldor D. Investigation of gasification kinetics of multi-component waste mixtures in a novel thermogravimetric flow reactor via gas analysis. Bioresour Technol 2022; 343:126044. [PMID: 34619322 DOI: 10.1016/j.biortech.2021.126044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 09/23/2021] [Accepted: 09/24/2021] [Indexed: 06/13/2023]
Abstract
A novel gasification fed-batch reactor enabling both thermogravimetric and gas analysis of large samples (up to tens of grams) was designed and tested. Air gasification experiments on food-court waste representative samples and its components were performed at 700 °C and 800 °C using ER = 0.3. At both temperatures, the lignocellulosics fraction produced highest H2 concentration (greater than 21% at 800 °C) while the plastic components generated less H2 regardless of process temperature (2.44%-7.08%). Synergistic effects of multiple components gasification with respect to H2 production was noticed through its non-linear evolution at 700 °C (ranging from 1.18% to 5.38%). A strong negative effect was observed at 800 °C; plastic addition reduced H2 production when combined with lignocellulosic and organic matter (1.02% to 9.73%). The same effects were observed for CH4 formation. This phenomenon was validated by kinetic analysis of decay curves of all components and their mixtures at the beginning of gasification in entire temperature region.
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Affiliation(s)
- Cosmin Mărculescu
- Faculty of Power Engineering, University POLITEHNICA of Bucharest, Romania
| | | | | | - Dorin Boldor
- Department of Biological & Agricultural Engineering, Louisiana State University Agricultural Center, 149 E. B. Doran, Baton Rouge, LA 70803, USA.
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Knipper P, Bégué T, Pasquesoone L, Guerre E, Khonsari R, Girard P, Berger A, Khachatryan L, Tchaparian M. [Plastic surgery and fighting: Our experience during Nagorno-Karabakh war in 2020]. ANN CHIR PLAST ESTH 2021; 66:201-209. [PMID: 33966906 DOI: 10.1016/j.anplas.2021.03.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 03/10/2021] [Indexed: 10/21/2022]
Abstract
INTRODUCTION This work relates the experience of three French surgical missions in the care of the war wounded during the armed conflict in Nagorno Karabakh which took place from September 27 to November 10, 2020. MATERIALS AND METHODS Three surgical missions were carried out in Armenia between October 2020 and January 2021. Surgeons intervened in different hospitals, at different times of the conflict and on various war wounds. RESULTS The presence of a plastic surgeon proved to be essential in the care of war wounded, especially in delayed emergency and secondary care. The ortho-plastic treatment offered during these missions has proven to be effective in the reconstruction of limbs. These missions made it possible to introduce the induced membrane technique of Masquelet AC in Armenia. During our visit to the Yerevan burn center, we mentioned the very probable use of white phosphorus as an etiology in several of the cases analyzed. CONCLUSION We relate the particular experience of civilian surgeons in the context of a modern armed conflict. The presence of a plastic surgeon proved to be indispensable in the care of war wounded and especially in their secondary reconstructions.
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Affiliation(s)
- P Knipper
- Service de chirurgie plastique, reconstructrice et esthétique, hôpital européen Georges-Pompidou, 20, rue Leblanc, 75015 Paris, France.
| | - T Bégué
- Service de chirurgie orthopédique, traumatologique et réparatrice, hôpital Antoine-Béclère, AP-HP, université Paris-Saclay, 157, rue de la Porte-de-Triviaux, 92140 Clamart, France
| | - L Pasquesoone
- Service de chirurgie plastique, reconstructrice et esthétique, hôpital Roger-Salengro, avenue Émile-Laine, 59037 Lille, France
| | - E Guerre
- Service de chirurgie orthopédique, hôpital Roger-Salengro, avenue Émile-Laine, 59037 Lille, France
| | - R Khonsari
- Service de chirurgie maxillo-faciale et chirurgie plastique, hôpital Necker-Enfants-Malades, 149, rue de Sèvres, 75015 Paris, France
| | - P Girard
- Service de chirurgie orthopédique et traumatologique, groupe hospitalier public du sud de l'Oise, site de Creil, boulevard Laennec, 60100 Creil, France
| | - A Berger
- Service de chirurgie digestive et obésité, hôpital Saint-Joseph, 185, rue Raymond-Losserand, 75014 Paris, France
| | - L Khachatryan
- Service de chirurgie vasculaire, hôpital européen Georges-Pompidou, 20, rue Leblanc, 75015 Paris, France
| | - M Tchaparian
- Service de traumatologie, hôpital Roger-Salengro, avenue Émile-Laine, 59037 Lille, France
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Hudzik JM, Barekati-Goudarzi M, Khachatryan L, Bozzelli JW, Ruckenstein E, Asatryan R. OH-Initiated Reactions of para-Coumaryl Alcohol Relevant to the Lignin Pyrolysis. Part II. Kinetic Analysis. J Phys Chem A 2020; 124:4875-4904. [DOI: 10.1021/acs.jpca.9b11894] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jason M. Hudzik
- Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, New Jersey 07102, United States
| | | | - Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Joseph W. Bozzelli
- Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, New Jersey 07102, United States
| | - Eli Ruckenstein
- Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14226, United States
| | - Rubik Asatryan
- Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14226, United States
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Hasan F, Khachatryan L, Lomnicki S. Comparative Studies of Environmentally Persistent Free Radicals on Total Particulate Matter Collected from Electronic and Tobacco Cigarettes. Environ Sci Technol 2020; 54:5710-5718. [PMID: 32267684 DOI: 10.1021/acs.est.0c00351] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In the current study, electron paramagnetic resonance (EPR) spectroscopy was employed to measure environmentally persistent free radicals (EPFRs) in the total particulate matter (TPM) of mainstream and sidestream TPM of conventional cigarettes and the TPM of e-cigarettes. Comparable concentrations of EPFRs were detected in both sidestream (8.05 ± 1.32) × 104 pmol/g and mainstream TPM (7.41 ± 0.85) × 104 pmol/g of conventional cigarettes. TPM exposure to air resulted in long-lived oxygen centered, secondary radicals with EPR g values of 2.0041 for mainstream and 2.0044 for sidestream. Surprisingly, despite no combustion process, the TPM from e-cigarettes (menthol flavor of NJOY and V2 brands) also contain EPFRs with g values of 2.0031-2.0033, characteristic of carbon centered radicals, while the radical signal in the vanilla flavor of V2 brand was remarkably similar to semiquinones in cigarette smoke with a higher g value (2.0063). The radical concentration in e-cigarettes was much lower as compared to tobacco TPM. Although the production of ROS generated by e-cigarettes is comparatively lower than ROS generated by conventional cigarettes, EPFRs in e-cigarettes appear to be more potent than those in tobacco TPM with respect to hydroxyl radical generation yield per unit EPFR. EPFRs in e-cigarette TPM may be a potential source of health impacts.
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Affiliation(s)
- Farhana Hasan
- Department of Environmental Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Slawo Lomnicki
- Department of Environmental Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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10
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Daniel D, Khachatryan L, Astete C, Asatryan R, Marculescu C, Boldor D. Sulfur contaminations inhibit depolymerization of Kraft lignin. ACTA ACUST UNITED AC 2019. [DOI: 10.1016/j.biteb.2019.100341] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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11
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Xu M, Wu T, Tang YT, Chen T, Khachatryan L, Iyer PR, Guo D, Chen A, Lyu M, Li J, Liu J, Li D, Zuo Y, Zhang S, Wang Y, Meng Y, Qi F. Environmentally persistent free radicals in PM 2.5: a review. ACTA ACUST UNITED AC 2019; 1:177-197. [PMID: 34308260 DOI: 10.1007/s42768-019-00021-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Environmentally persistent free radicals (EPFRs) are a new class of pollutants that are long-lived in fine particles (PM2.5), i.e., their 1/e lifetime ranges from days to months (or even infinite). They are capable of producing harmful reactive oxygen species such as hydroxyl radicals. The redox cycling of EPFRs is considered as an important pathway for PM2.5 to induce oxidative stress inside the humans, causing adverse health effects such as respiratory and cardiovascular diseases. Consequently, research regarding their toxicity, formation and environmental occurrences in PM2.5 has attracted increasing attentions globally during the past two decades. However, literature data in this field remain quite limited and discrete. Hence, an extensive review is urgently needed to summarize the current understanding of this topic. In this work, we systematically reviewed the analytical methods and environmental occurrences, e.g., types, concentrations, and decay behaviors, as well as possible sources of EPFRs in PM2.5. The types of pretreatment methods, g-values of common EPFRs and categories of decay processes were discussed in detail. Moreover, great efforts were made to revisit the original data of the published works of EPFRs in airborne particulate matter and provided additional useful information for comparison where possible, e.g., their mean and standard deviation of g-values, line widths (ΔH p-p), and concentrations. Finally, possible research opportunities were highlighted to further advance our knowledge of this emerging issue.
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Affiliation(s)
- Mengxia Xu
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China.,New Materials Institute, University of Nottingham Ningbo China, Ningbo 315100, China
| | - Tao Wu
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China.,New Materials Institute, University of Nottingham Ningbo China, Ningbo 315100, China
| | - Yu-Ting Tang
- School of Geographical Sciences, University of Nottingham Ningbo China, Ningbo 315100, China
| | - Tong Chen
- State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, Hangzhou 310027, China
| | - Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Poornima Ramesh Iyer
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China
| | - Dengting Guo
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China
| | - Anran Chen
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China
| | - Miao Lyu
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China
| | - Jinhu Li
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China
| | - Jiaqi Liu
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China
| | - Dan Li
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China
| | - Yuxin Zuo
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China
| | - Shihan Zhang
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China
| | - Yiran Wang
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China
| | - Yining Meng
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China
| | - Fei Qi
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China
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12
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Asatryan R, Hudzik JM, Bozzelli JW, Khachatryan L, Ruckenstein E. OH-Initiated Reactions of p-Coumaryl Alcohol Relevant to the Lignin Pyrolysis. Part I. Potential Energy Surface Analysis. J Phys Chem A 2019; 123:2570-2585. [DOI: 10.1021/acs.jpca.9b00185] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rubik Asatryan
- Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14226, United States
| | - Jason M. Hudzik
- Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, New Jersey 07102, United States
| | - Joseph W. Bozzelli
- Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, New Jersey 07102, United States
| | - Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Eli Ruckenstein
- Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14226, United States
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13
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Vejerano EP, Rao G, Khachatryan L, Cormier SA, Lomnicki S. Environmentally Persistent Free Radicals: Insights on a New Class of Pollutants. Environ Sci Technol 2018; 52:2468-2481. [PMID: 29443514 PMCID: PMC6497067 DOI: 10.1021/acs.est.7b04439] [Citation(s) in RCA: 99] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Environmentally persistent free radicals, EPFRs, exist in significant concentration in atmospheric particulate matter (PM). EPFRs are primarily emitted from combustion and thermal processing of organic materials, in which the organic combustion byproducts interact with transition metal-containing particles to form a free radical-particle pollutant. While the existence of persistent free radicals in combustion has been known for over half-a-century, only recently that their presence in environmental matrices and health effects have started significant research, but still in its infancy. Most of the experimental studies conducted to understand the origin and nature of EPFRs have focused primarily on nanoparticles that are supported on a larger micrometer-sized particle that mimics incidental nanoparticles formed during combustion. Less is known on the extent by which EPFRs may form on engineered nanomaterials (ENMs) during combustion or thermal treatment. In this critical and timely review, we summarize important findings on EPFRs and discuss their potential to form on pristine ENMs as a new research direction. ENMs may form EPFRs that may differ in type and concentration compared to nanoparticles that are supported on larger particles. The lack of basic data and fundamental knowledge about the interaction of combustion byproducts with ENMs under high-temperature and oxidative conditions present an unknown environmental and health burden. Studying the extent of ENMs on catalyzing EPFRs is important to address the hazards of atmospheric PM fully from these emerging environmental contaminants.
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Affiliation(s)
- Eric P. Vejerano
- Center for Environmental Nanoscience and Risk, Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia South Carolina 29208, United States
- Corresponding Author: Phone: (803) 777 6360;
| | - Guiying Rao
- Center for Environmental Nanoscience and Risk, Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia South Carolina 29208, United States
| | - Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Stephania A. Cormier
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
- Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana 70803, United States
| | - Slawo Lomnicki
- Department of Environmental Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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14
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Asatryan R, Bennadji H, Bozzelli JW, Ruckenstein E, Khachatryan L. Molecular Products and Fundamentally Based Reaction Pathways in the Gas-Phase Pyrolysis of the Lignin Model Compound p-Coumaryl Alcohol. J Phys Chem A 2017; 121:3352-3371. [PMID: 28406634 DOI: 10.1021/acs.jpca.7b01656] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The fractional pyrolysis of lignin model compound para-coumaryl alcohol (p-CMA) containing a propanoid side chain and a phenolic OH group was studied using the System for Thermal Diagnostic Studies at temperatures from 200 to 900 °C, in order to gain mechanistic insight into the role of large substituents in high-lignin feedstocks pyrolysis. Phenol and its simple derivatives p-cresol, ethyl-, propenyl-, and propyl-phenols were found to be the major products predominantly formed at low pyrolysis temperatures (<500 °C). A cryogenic trapping technique was employed combined with EPR spectroscopy to identify the open-shell intermediates registered at pyrolysis temperatures above 500 °C. These were characterized as radical mixtures primarily consisting of oxygen-linked conjugated radicals. A comprehensive potential energy surface analysis of p-CMA and p-CMA + H atom systems was performed using various DFT protocols to examine the possible role of concerted molecular eliminations and free-radical mechanisms in the formation of major products. Other significant unimolecular concerted reactions along with formation and decomposition of primary radicals are also described and evaluated. The calculations suggest that a set of the chemically activated secondary radical channels is relevant to the low temperature product formation under fractional pyrolysis conditions.
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Affiliation(s)
- Rubik Asatryan
- Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14226, United States
| | - Hayat Bennadji
- Department of Environmental Sciences, Louisiana State University , Baton Rouge, Louisiana 70808, United States
| | - Joseph W Bozzelli
- Department of Chemistry and Environmental Science, New Jersey Institute of Technology , Newark, New Jersey 07102, United States
| | - Eli Ruckenstein
- Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14226, United States
| | - Lavrent Khachatryan
- Department of Chemistry, Louisiana State University , Baton Rouge, Louisiana 70803, United States
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15
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Khachatryan L, Xu MX, Wu AJ, Pechagin M, Asatryan R. Radicals and molecular products from the gas-phase pyrolysis of lignin model compounds. Cinnamyl alcohol. J Anal Appl Pyrolysis 2016; 121:75-83. [PMID: 28344372 PMCID: PMC5363761 DOI: 10.1016/j.jaap.2016.07.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The experimental results on detection and identification of intermediate radicals and molecular products from gas-phase pyrolysis of cinnamyl alcohol (CnA), the simplest non-phenolic lignin model compound, over the temperature range of 400-800 °C are reported. The low temperature matrix isolation - electron paramagnetic resonance (LTMI-EPR) experiments along with the theoretical calculations, provided evidences on the generation of the intermediate carbon and oxygen centered as well as oxygen-linked, conjugated radicals. A mechanistic analysis is performed based on density functional theory to explain formation of the major products from CnA pyrolysis; cinnamaldehyde, indene, styrene, benzaldehyde, 1-propynyl benzene, and 2-propenyl benzene. The evaluated bond dissociation patterns and unimolecular decomposition pathways involve dehydrogenation, dehydration, 1,3-sigmatropic H-migration, 1,2-hydrogen shift, C-O and C-C bond cleavage processes.
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Affiliation(s)
- Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA
- Corresponding author. (L. Khachatryan)
| | - Meng-xia Xu
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Ang-jian Wu
- State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, Hangzhou 310027, China
| | - Mikhail Pechagin
- Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
| | - Rubik Asatryan
- Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
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16
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Abstract
The intermediate radicals produced in the gas-phase pyrolysis of one of the main building blocks of lignin - p-coumaryl alcohol (p-CMA) - were investigated using the low temperature matrix isolation technique interfaced with electron paramagnetic resonance spectroscopy (LTMI-EPR). An anisotropic EPR spectrum characterized by a high g-value (>2.0080) and a relatively low saturation coefficient (∼1.40) throughout the high pyrolytic temperature region (700 to 1000 °C) was observed. Theoretical calculations revealed plausible decomposition pathways for p-CMA comprising highly delocalized aromatic radicals. The results provide evidence for a dominant role of oxygen-centered radicals during the pyrolysis of p-CMA.
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Affiliation(s)
- Meng-Xia Xu
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Alexander Baev
- Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
| | - Rubik Asatryan
- Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
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17
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Nwosu UG, Khachatryan L, Youm SG, Roy A, Dela Cruz ALN, Nesterov EE, Dellinger B, Cook RL. Model System Study of Environmentally Persistent Free Radicals Formation in a Semiconducting Polymer Modified Copper Clay System at Ambient Temperature. RSC Adv 2016; 6:43453-43462. [PMID: 28670444 DOI: 10.1039/c6ra08051k] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
This paper systematically investigates how environmentally persistent free radicals (EPFRs) are formed in a phenol contaminated model soil. Poly-p-phenylene (PPP) modified and copper-loaded montmorillonite (MMT) clays were developed and used as models of soil organic matter and the clay mineral component, respectively, with phenol being employed as a precursor pollutant. The polymer modification of the clays was carried out via surface-confined Kumada catalyst-transfer chain-growth polymerization. The presence and location of the polymer were confirmed by a combination of thermogravimetric analysis (TGA), Raman spectroscopy, and X-ray diffraction data. EPFRs were formed by the Cu(II)-clay (Cu(II)CaMMT) and poly-p-phenylene-Cu(II)clay (PPP-Cu(II)CaMMT) composite systems under environmentally relevant conditions. The g-factor and concentration of EPFRs formed by the Cu(II)CaMMT and PPP-Cu(II)CaMMT systems were found to be 2.0034 and 1.22 × 1017 spins/g and 2.0033 and 1.58 × 1017spins/g, respectively. These g-factors are consistent with the formation of phenoxyl radicals. Extended X-Ray absorption fine structure (EXAFS) analysis shows that there are distinct differences in the local stuctures of the phenoxyl radicals associated with only the Cu(II) redox centers and those formed in the presences of the PPP polymer. X-ray absorption near edge spectroscopy (XANES) results provided evidence for the reduction of Cu(II) to Cu(I) in the EPFR forming process. The 1/e lifetimes of the formed EPFRs revealed a decay time of ~20 h for the Cu(II)CaMMT system and a two-step decay pattern for the PPP-Cu(II)CaMMT system with decay times of ~13.5 h and ~55.6 h. Finally, the generation of reactive oxygen species (hydroxyl radical; •OH) by these clay systems was also investigated, with higher concentrations of •OH detected for the phenol-dosed Cu(II)CaMMT and PPP-Cu(II)CaMMT systems, compared to the non-EPFR containing undosed PPP-Cu(II)CaMMT system.
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Affiliation(s)
- Ugwumsinachi G Nwosu
- Louisiana State University, Department of Chemistry, Baton Rouge, LA 70803, United States.,Louisiana State University Superfund Research Center, Baton Rouge, Louisiana 70803, United States
| | - Lavrent Khachatryan
- Louisiana State University, Department of Chemistry, Baton Rouge, LA 70803, United States.,Louisiana State University Superfund Research Center, Baton Rouge, Louisiana 70803, United States
| | - Sang Gil Youm
- Louisiana State University, Department of Chemistry, Baton Rouge, LA 70803, United States
| | - Amitava Roy
- Center for Advanced Microstructures & Devices, Louisiana State University, 6980 Jefferson Highway, Baton Rouge, Louisiana 70806, United States
| | - Albert Leo N Dela Cruz
- Louisiana State University Superfund Research Center, Baton Rouge, Louisiana 70803, United States
| | - Evgueni E Nesterov
- Louisiana State University, Department of Chemistry, Baton Rouge, LA 70803, United States
| | - Barry Dellinger
- Louisiana State University, Department of Chemistry, Baton Rouge, LA 70803, United States.,Louisiana State University Superfund Research Center, Baton Rouge, Louisiana 70803, United States
| | - Robert L Cook
- Louisiana State University, Department of Chemistry, Baton Rouge, LA 70803, United States.,Louisiana State University Superfund Research Center, Baton Rouge, Louisiana 70803, United States
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18
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Kibet JK, Khachatryan L, Dellinger B. Phenols from pyrolysis and co-pyrolysis of tobacco biomass components. Chemosphere 2015; 138:259-65. [PMID: 26091866 DOI: 10.1016/j.chemosphere.2015.06.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 05/15/2015] [Accepted: 06/01/2015] [Indexed: 06/04/2023]
Abstract
Phenol and its derivatives (phenol, o-, m-, p-cresols, catechol, hydroquinone, methoxy substituted phenols, etc. referred to as phenolic compounds or phenols) are well-known toxicants that exist in the environment and affect both human and natural ecosystems. This study explores quantitatively the yields of phenolic compounds from the thermal degradation (pyrolysis and oxidative pyrolysis) of common tobacco biomass components (lignin, tyrosine, ethyl cellulose, sodium alginate, and laminarin) as well as some mixtures (lignin/tyrosine, ethyl cellulose/tyrosine and sodium alginate/tyrosine) considered important in high temperature cooking, tobacco smoking, and forest fires. Special attention has been given to binary mixtures including those containing tyrosine-pyrolysis of binary mixtures of tyrosine with lignin and ethyl cellulose results in significant reductions in the yields of majority phenols relative to those from the thermal degradation of tyrosine. These results imply that the significant reductions of phenol yields in mixtures are not only dependent upon the mass fractions of the components but also the synergetic inhibition effect of biomass components on the thermal degradation of tyrosine. A mechanistic description of this phenomenon is suggested. The results may also be implied in tobacco industry that the cigarette paper (as ethyl cellulose derivative) may play a critical role in reducing the concentration of phenolic compounds released during tobacco burning.
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Affiliation(s)
- Joshua K Kibet
- Department of Chemistry, Egerton University, P.O. Box 536, Egerton, Kenya
| | - Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - Barry Dellinger
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA
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19
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Herring MP, Khachatryan L, Dellinger B. Speciation of Iron (III) Oxide Nanoparticles and Other Paramagnetic Intermediates during High-Temperature Oxidative Pyrolysis of 1-Methylnaphthalene. World Acad Sci Eng Technol 2015; 9:804-812. [PMID: 26413257 PMCID: PMC4581597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Low Temperature Matrix Isolation - Electron Paramagnetic Resonance (LTMI-EPR) Spectroscopy was utilized to identify the species of iron oxide nanoparticles generated during the oxidative pyrolysis of 1-methylnaphthalene (1-MN). The otherwise gas-phase reactions of 1--MN were impacted by a polypropylenimine tetra-hexacontaamine dendrimer complexed with iron (III) nitrate nonahydrate diluted in air under atmospheric conditions. The EPR fine structure of Fe (III)2O3 nanoparticles clusters, characterized by g-factors of 2.00, 2.28, 3.76 and 4.37 were detected on a cold finger maintained at 77 K after accumulation over a multitude of experiments. Additionally, a high valence Fe (IV) paramagnetic intermediate and superoxide anion-radicals, O2•- adsorbed on nanoparticle surfaces in the form of Fe (IV) --- O2•- were detected from the quenching area of Zone 1 in the gas-phase.
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Affiliation(s)
| | - Lavrent Khachatryan
- LSU, Department of Chemistry, Baton Rouge, LA, 70803 USA (phone: 225 578 4417; )
| | - Barry Dellinger
- LSU, Department of Chemistry, Baton Rouge, LA, 70803 USA ( )
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20
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Khachatryan L, McFerrin C, Hall R, Dellinger B. Environmentally persistent free radicals (EPFRs). 3. Free versus bound hydroxyl radicals in EPFR aqueous solutions. Environ Sci Technol 2014; 48:9220-6. [PMID: 25036238 PMCID: PMC4140529 DOI: 10.1021/es501158r] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 07/08/2014] [Accepted: 07/18/2014] [Indexed: 05/19/2023]
Abstract
Additional experimental evidence is presented for in vitro generation of hydroxyl radicals because of redox cycling of environmentally persistent free radicals (EPFRs) produced after adsorption of 2-monochlorophenol at 230 °C (2-MCP-230) on copper oxide supported by silica, 5% Cu(II)O/silica (3.9% Cu). A chemical spin trapping agent, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy was employed. Experiments in spiked O(17) water have shown that ∼15% of hydroxyl radicals formed as a result of redox cycling. This amount of hydroxyl radicals arises from an exogenous Fenton reaction and may stay either partially trapped on the surface of particulate matter (physisorbed or chemisorbed) or transferred into solution as free OH. Computational work confirms the highly stable nature of the DMPO-OH adduct, as an intermediate produced by interaction of DMPO with physisorbed/chemisorbed OH (at the interface of solid catalyst/solution). All reaction pathways have been supported by ab initio calculations.
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Affiliation(s)
- Lavrent Khachatryan
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
- Telephone: 225-578-4417. E-mail:
| | - Cheri
A. McFerrin
- Department
of Natural Sciences and Mathematics, Dominican
University of California, San Rafael, California 94901, United States
| | - Randall
W. Hall
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
- Department
of Natural Sciences and Mathematics, Dominican
University of California, San Rafael, California 94901, United States
| | - Barry Dellinger
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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21
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Gehling W, Khachatryan L, Dellinger B. Hydroxyl radical generation from environmentally persistent free radicals (EPFRs) in PM2.5. Environ Sci Technol 2014; 48:4266-72. [PMID: 24004313 PMCID: PMC4308723 DOI: 10.1021/es401770y] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Hydroxyl radicals were generated from an aqueous suspension of ambient PM2.5 and detected utilizing 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap coupled with electron paramagnetic resonance (EPR) spectroscopy. Results from this study suggested the importance of environmentally persistent free radicals (EPFRs) in PM2.5 to generate significant levels of ·OH without the addition of H2O2. Particles for which the EPFRs were allowed to decay over time induced less hydroxyl radical. Additionally, higher particle concentrations produced more hydroxyl radical. Some samples did not alter hydroxyl radical generation when the solution was purged by air. This is ascribed to internal, rather than external surface associated EPFRs.
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22
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Kiruri LW, Khachatryan L, Dellinger B, Lomnicki S. Effect of copper oxide concentration on the formation and persistency of environmentally persistent free radicals (EPFRs) in particulates. Environ Sci Technol 2014; 48:2212-7. [PMID: 24437381 PMCID: PMC3983329 DOI: 10.1021/es404013g] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Revised: 12/04/2013] [Accepted: 01/17/2014] [Indexed: 05/19/2023]
Abstract
Environmentally persistent free radicals (EPFRs) are formed by the chemisorption of substituted aromatics on metal oxide surfaces in both combustion sources and superfund sites. The current study reports the dependency of EPFR yields and their persistency on metal loading in particles (0.25, 0.5, 0.75, 1, 2, and 5% CuO/silica). The EPFRs were generated through exposure of particles to three adsorbate vapors at 230 °C: phenol, 2-monochlorophenol (2-MCP), and dichlorobenzene (DCBz). Adsorption resulted in the formation of surface-bound phenoxyl- and semiquinoine-type radicals with characteristic EPR spectra displaying a g value ranging from ∼ 2.0037 to 2.006. The highest EPFR yield was observed for CuO concentrations between 1 and 3% in relation to MCP and phenol adsorption. However, radical density, which is expressed as the number of radicals per copper atom, was highest at 0.75-1% CuO loading. For 1,2-dichlorobenzene adsorption, radical concentration increased linearly with decreasing copper content. At the same time, a qualitative change in the radicals formed was observed--from semiquinone to chlorophenoxyl radicals. The two longest lifetimes, 25 and 23 h, were observed for phenoxyl-type radicals on 0.5% CuO and chlorophenoxyl-type radicals on 0.75% CuO, respectively.
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23
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Herring P, Khachatryan L, Lomnicki S, Dellinger B. Paramagnetic centers in particulate formed from the oxidative pyrolysis of 1-methylnaphthalene in the presence of Fe(III) 2O 3 nanoparticles. Combust Flame 2013; 160:2996-3003. [PMID: 25673882 PMCID: PMC4321761 DOI: 10.1016/j.combustflame.2013.06.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The identity of radical species associated with particulate formed from the oxidative pyrolysis of 1-methylnaphthalene (1-MN) was investigated using low temperature matrix isolation electron paramagnetic resonance spectroscopy (LTMI-EPR), a specialized technique that provided a method of sampling and analysis of the gas-phase paramagnetic components. A superimposed EPR signal was identified to be a mixture of organic radicals (carbon and oxygen-centered) and soot. The carbon-centered radicals were identified as a mixture of the resonance-stabilized indenyl, cyclopentadienyl, and naphthalene 1-methylene radicals through the theoretical simulation of the radical's hyperfine structure. Formation of these radical species was promoted by the addition of Fe(III)2O3 nanoparticles. Enhanced formation of resonance stabilized radicals from the addition of Fe(III)2O3 nanoparticles can account for the observed increased sooting tendency associated with Fe(III)2O3 nanoparticle addition.
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Affiliation(s)
- Paul Herring
- Louisiana State University, Department of Chemistry, Baton Rouge, LA 70803, USA
| | - Lavrent Khachatryan
- Louisiana State University, Department of Chemistry, Baton Rouge, LA 70803, USA
| | - Slawomir Lomnicki
- Louisiana State University, Department of Chemistry, Baton Rouge, LA 70803, USA
| | - Barry Dellinger
- Louisiana State University, Department of Chemistry, Baton Rouge, LA 70803, USA
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Maskos Z, Khachatryan L, Dellinger B. Role of the Filters in the Formation and Stabilization of Semiquinone Radicals Collected from Cigarette Smoke. Energy Fuels 2013; 27:10.1021/ef4010253. [PMID: 24265513 PMCID: PMC3831374 DOI: 10.1021/ef4010253] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The fractional pyrolysis of Bright tobacco was performed in nitrogen atmosphere over the temperature range of 240 - 510 °C in a specially constructed, high temperature flow reactor system. Electron paramagnetic resonance (EPR) spectroscopy was used to analyze the free radicals in the initially produced total particular matter (TPM) and in TPM after exposure to ambient air (aging). Different filters have been used to collect TPM from tobacco smoke: cellulosic, cellulose nitrate, cellulose acetate, nylon, Teflon and Cambridge. The collection of the primary radicals (measured immediately after collection of TPM on filters), the formation and stabilization of the secondary radicals (defined as radicals formed during aging of TPM samples on the filters) depend significantly on the material of the filter. A mechanistic explanation about different binding capability of the filters decreasing in the order: cellulosic < cellulose nitrate < cellulose acetate < nylon ~ teflon is presented. Different properties were observed for the Cambridge filter. Specific care must be taken using the filters for identification of radicals from tobacco smoke to avoid artifacts in each case.
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Affiliation(s)
- Zofia Maskos
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana
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25
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Abstract
The thermal behavior of glutamic acid was investigated in N2 and 4% O2 in N2 under flow reactor conditions at a constant residence time of 0.2 s, within a total pyrolysis time of 3 min at 1 atm. The identification of the main pyrolysis products has been reported. Accordingly, the principal products for pyrolysis in order of decreasing abundance were succinimide, pyrrole, acetonitrile, and 2-pyrrolidone. For oxidative pyrolysis, the main products were succinimide, propiolactone, ethanol, and hydrogen cyanide. Whereas benzene, toluene, and a few low molecular weight hydrocarbons (propene, propane, 1-butene, and 2-butene) were detected during pyrolysis, no polycyclic aromatic hydrocarbons (PAHs) were detected. Oxidative pyrolysis yielded low molecular weight hydrocarbon products in trace amounts. The mechanistic channels describing the formation of the major product succinimide have been explored. The detection of succinimide (major product) and maleimide (minor product) from the thermal decomposition of glutamic acid has been reported for the first time in this study. Toxicological implications of some reaction products (HCN, acetonitrile, and acyrolnitrile), which are believed to form during heat treatment of food, tobacco burning, and drug processing, have been discussed in relation to the thermal degradation of glutamic acid.
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Affiliation(s)
- Joshua K Kibet
- Department of Chemistry, Louisiana State University , Baton Rouge, Louisiana 70803, United States
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Kibet JK, Khachatryan L, Dellinger B. Molecular products from the pyrolysis and oxidative pyrolysis of tyrosine. Chemosphere 2013; 91:1026-1034. [PMID: 23490178 DOI: 10.1016/j.chemosphere.2013.01.071] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 01/07/2013] [Accepted: 01/16/2013] [Indexed: 06/01/2023]
Abstract
The thermal degradation of tyrosine at a residence time of 0.2s was conducted in a tubular flow reactor in flowing N2 and 4% O2 in N2 for a total pyrolysis time of 3min. The fractional pyrolysis technique, in which the same sample was heated continuously at each pyrolysis temperature, was applied. Thermal decomposition of tyrosine between 350 and 550°C yielded predominantly phenolic compounds (phenol, p-cresol, and p-tyramine), while decomposition between 550 and 800°C yielded hydrocarbons such as benzene, toluene, and ethyl benzene as the major reaction products. For the first time, the identification of p-tyramine, a precursor for the on of formation of p-tyramine and its degradation to phenol and p-cresol, and toxicological discussion of some of the harmful reaction products is also presented.
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Affiliation(s)
- Joshua K Kibet
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA
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Abstract
Thermal degradation of lignin under two reaction regimes (pyrolysis in N(2) and oxidative pyrolysis in 4% O(2) in N(2)) has been investigated in a tubular, isothermal, flow-reactor over the temperature range 200-900 °C at a residence time of 0.2 s. Two experimental protocols were adopted: (1) Partial pyrolysis in which the same lignin sample was continuously pyrolyzed at each temperature and (2) conventional pyrolysis, in which new lignin samples were pyrolyzed at each pyrolysis temperature. The results identified common relationships between the two modes of experiments, as well as some differences. The majority of products from partial pyrolysis peaked between 300 and 500 °C, whereas for conventional pyrolysis reaction products peaked between 400 and 500 °C. The principal products were syringol (2,6-dimethoxy phenol), guaiacol (2-methoxy phenol), phenol, and catechol. Of the classes of compounds analyzed, the phenolic compounds were the most abundant, contributing over 40% of the total compounds detected. Benzene, styrene, and p-xylene were formed in significant amounts throughout the entire temperature range. Interestingly, six ringed polycyclic aromatic hydrocarbons were formed during partial pyrolysis. Oxidative pyrolysis did not result in large differences from pyrolysis; the main products still were syringol, guaiacol, phenol, the only significant difference being the product distribution peaked between 200 and 400 °C. For the first time, low temperature matrix isolation electron paramagnetic resonance was successfully interfaced with the pyrolysis reactor to elucidate the structures of the labile reaction intermediates. The EPR results suggested the presence of methoxyl, phenoxy, and substituted phenoxy radicals as precursors for formation of major products; syringol, guaiacol, phenols, and substituted phenols.
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Affiliation(s)
- J Kibet
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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Astete CE, Dolliver D, Whaley M, Khachatryan L, Sabliov CM. Antioxidant poly(lactic-co-glycolic) acid nanoparticles made with α-tocopherol-ascorbic acid surfactant. ACS Nano 2011; 5:9313-9325. [PMID: 22017172 DOI: 10.1021/nn102845t] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The goal of the study was to synthesize a surfactant made of α-tocopherol (vitamin E) and ascorbic acid (vitamin C) of antioxidant properties dubbed as EC, and to use this surfactant to make poly(lactic-co-glycolic) acid (PLGA) nanoparticles. Self-assembled EC nanostructures and PLGA-EC nanoparticles were made by nanoprecipitation, and their physical properties (size, size distribution, morphology) were studied at different salt concentrations, surfactant concentrations, and polymer/surfactant ratios. EC surfactant was shown to form self-assembled nanostructures in water with a size of 22 to 138 nm in the presence of sodium chloride, or 12 to 31 nm when synthesis was carried out in sodium bicarbonate. Polymeric PLGA-EC nanoparticles presented a size of 90 to 126 nm for 40% to 120% mass ratio PLGA to surfactant. For the same mass ratios, the PLGA-Span80 formed particles measured 155 to 216 nm. Span80 formed bilayers, whereas EC formed monolayers at the interfaces. PLGA-EC nanoparticles and EC showed antioxidant activity based on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay measurements using UV and EPR techniques, antioxidant activity which is not characteristic to commercially available Span80. The thiobarbituric acid reactive substances (TBARS) assay for lipid peroxidation showed that PLGA nanoparticles with EC performed better as antioxidants than the EC nanoassembly or the free vitamin C. Nanoparticles were readily internalized by HepG2 cells and were localized in the cytoplasm. The newly synthesized EC surfactant was therefore found successful in forming uniform, small size polymeric nanoparticles of intrinsic antioxidant properties.
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Affiliation(s)
- Carlos E Astete
- Biological and Agricultural Engineering Department, Louisiana State University Agricultural Center, United States
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Khachatryan L, Dellinger B. Environmentally persistent free radicals (EPFRs)-2. Are free hydroxyl radicals generated in aqueous solutions? Environ Sci Technol 2011; 45:9232-9. [PMID: 21942783 PMCID: PMC3236504 DOI: 10.1021/es201702q] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
A chemical spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy was employed to measure the production of hydroxyl radical (·OH) in aqueous suspensions of 5% Cu(II)O/silica (3.9% Cu) particles containing environmentally persistent free radicals (EPFRs) of 2-monochlorophenol (2-MCP). The results indicate: (1) a significant differences in accumulated DMPO-OH adducts between EPFR containing particles and non-EPFR control samples, (2) a strong correlation between the concentration of DMPO-OH adducts and EPFRs per gram of particles, and (3) a slow, constant growth of DMPO-OH concentration over a period of days in solution containing 50 μg/mL EPFRs particles + DMPO (150 mM) + reagent balanced by 200 μL phosphate buffered (pH = 7.4) saline. However, failure to form secondary radicals using standard scavengers, such as ethanol, dimethylsulfoxide, sodium formate, and sodium azide, suggests free hydroxyl radicals may not have been generated in solution. This suggests surface-bound, rather than free, hydroxyl radicals were generated by a surface catalyzed-redox cycle involving both the EPFRs and Cu(II)O. Toxicological studies clearly indicate these bound free radicals promote various types of cardiovascular and pulmonary disease normally attributed to unbound free radicals; however, the exact chemical mechanism deserves further study in light of the implication of formation of bound, rather than free, hydroxyl radicals.
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Affiliation(s)
- Lavrent Khachatryan
- Louisiana State University, Department of Chemistry, Baton Rouge, Louisiana 70803, United States
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Khachatryan L, Vejerano E, Lomnicki S, Dellinger B. Environmentally persistent free radicals (EPFRs). 1. Generation of reactive oxygen species in aqueous solutions. Environ Sci Technol 2011; 45:8559-66. [PMID: 21823585 PMCID: PMC3230252 DOI: 10.1021/es201309c] [Citation(s) in RCA: 174] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Reactive oxygen species (ROS) generated by environmentally persistent free radicals (EPFRs) of 2-monochlorophenol, associated with CuO/silica particles, were detected using the chemical spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy. Yields of hydroxyl radical ((•)OH), superoxide anion radical (O(2)(•-)), and hydrogen peroxide (H(2)O(2)) generated by EPFR-particle systems were reported. Failure to trap superoxide radicals in aqueous solvent, formed from reaction of EPFRs with molecular oxygen, results from fast transformation of the superoxide to hydrogen peroxide. However, formation of superoxide as an intermediate product in hydroxyl radical formation in aprotic solutions of dimethyl sulfoxide (DMSO) and acetonitrile (AcN) was observed. Experiments with superoxide dismutase (SOD) and catalase (CAT) confirmed formation of superoxide and hydrogen peroxide, respectively, in the presence of EPFRs. The large number of hydroxyl radicals formed per EPFR and monotonic increase of the DMPO-OH spin adduct concentration with incubation time suggest a catalytic cycle of ROS formation.
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Affiliation(s)
- Lavrent Khachatryan
- Department of Chemistry and LSU Superfund Research Center, Louisiana State University , Baton Rouge, Louisiana 70803, United States
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Simonyan L, Simonyan L, Khachatryan L. CHANGES OF PARAMETERS OF COAGULATION IN PATIENTS WITH HEART FAILURE TREATED WITH FILTRATION PLASMAPHERESIS. J Hypertens 2011. [DOI: 10.1097/00004872-201106001-01590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Khachatryan L, Asatryan R, McFerrin C, Adounkpe J, Dellinger B. Radicals from the gas-phase pyrolysis of catechol. 2. Comparison of the pyrolysis of catechol and hydroquinone. J Phys Chem A 2011; 114:10110-6. [PMID: 20731470 DOI: 10.1021/jp1054588] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Formation of radicals from the pyrolysis of catechol (CT) and hydroquinone (HQ) over a temperature range of 350-900 °C was studied using low-temperature matrix isolation electron paramagnetic resonance (LTMI EPR) spectroscopy. Comparative analysis of the pyrolysis mechanisms of these isomeric compounds was performed, and the role of semiquinone-type carrier radicals was studied. Pathways of unimolecular decomposition of intermediate radicals and molecular products were identified from the examination of the potential energy surface of catechol calculated at B3LYP hybrid density functional theory and composite CBS-QB3 levels. The results were compared with the experimental observations and mechanistic pathways previously developed for the pyrolysis of hydroquinone.
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Affiliation(s)
- Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
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Khachatryan L, Adounkpe J, Asatryan R, Dellinger B. Radicals from the Gas-Phase Pyrolysis of Catechol: 1. o-Semiquinone and ipso-Catechol Radicals. J Phys Chem A 2010; 114:2306-12. [DOI: 10.1021/jp908243q] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, New Jersey 07102
| | - Julien Adounkpe
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, New Jersey 07102
| | - Rubik Asatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, New Jersey 07102
| | - Barry Dellinger
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, New Jersey 07102
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Khachatryan L, Burcat A, Dellinger B. The role of chlorine atoms and hydroxyl radicals in the formation of PCDDs from the oxidative pyrolysis of 2,4,6-trichlorophenol. INT J CHEM KINET 2009. [DOI: 10.1002/kin.20461] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Sabliov CM, Fronczek C, Astete CE, Khachaturyan M, Khachatryan L, Leonardi C. Effects of Temperature and UV Light on Degradation of α-Tocopherol in Free and Dissolved Form. J AM OIL CHEM SOC 2009. [DOI: 10.1007/s11746-009-1411-6] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Khachatryan L, Adounkpe J, Dellinger B. Formation of Phenoxy and Cyclopentadienyl Radicals from the Gas-Phase Pyrolysis of Phenol. J Phys Chem A 2007; 112:481-7. [DOI: 10.1021/jp073999m] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Khachatryan L, Lomnicki S, Dellinger B. An expanded reaction kinetic model of the CuO surface-mediated formation of PCDD/F from pyrolysis of 2-chlorophenol. Chemosphere 2007; 68:1741-50. [PMID: 17509655 PMCID: PMC4273312 DOI: 10.1016/j.chemosphere.2007.03.042] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Revised: 11/15/2006] [Accepted: 03/26/2007] [Indexed: 05/15/2023]
Abstract
An expanded reaction kinetic model, including 17 surface reactions, is proposed to explain the yields of PCDD/F obtained in an experimental study of the reaction of 2-chlorophenol over a CuO/silica surface. The mechanism is loosely based on the gas-phase mechanism for PCDD/F formation widely discussed in the literature. The principal differences are the impact of chemisorption of 2-chlorophenols to metal oxides on radical formation and the steric hindrance of oxygen-centered radicals on the surface inhibiting radical-radical reaction pathways that lead to formation of dibenzo-p-dioxin (DD). Gas-phase molecule-surface-bound adsorbate reactions are the preferred route of DD formation, while radical-radical surface reactions are the main channel for dichloro-dibenzofuran (DCDF) formation. These results suggest that the Langmuir-Hinshelwood (LH) mechanism, involving radical-radical surface reactions, and the Eley-Rideal mechanism, involving a gas-phase molecule and surface-bound adsorbate, are responsible for PCDF and PCDD formation on surfaces, respectively. The calculated yields of DCDF and DD are in reasonable agreement with experimental results.
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Affiliation(s)
- Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, United States
| | - Slawo Lomnicki
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, United States
| | - Barry Dellinger
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, United States
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Dellinger B, Lomnicki S, Khachatryan L, Maskos Z, Hall RW, Adounkpe J, McFerrin C, Truong H. Formation and stabilization of persistent free radicals. Proc Combust Inst 2007; 31:521-528. [PMID: 25598747 PMCID: PMC4295210 DOI: 10.1016/j.proci.2006.07.172] [Citation(s) in RCA: 183] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We demonstrate that stable and relatively unreactive "environmentally persistent free radicals (PFRs)" can be readily formed in the post-flame and cool-zone regions of combustion systems and other thermal processes. These resonance-stabilized radicals, including semiquinones, phenoxyls, and cyclopentadienyls, can be formed by the thermal decomposition of molecular precursors including catechols, hydroquinones and phenols. Association with the surfaces of fine particles imparts additional stabilization to these radicals such that they can persist almost indefinitely in the environment. A mechanism of chemisorption and electron transfer from the molecular adsorbate to a redox-active transition metal or other receptor is shown through experiment, and supported by molecular orbital calculations, to result in PFR formation. Both oxygen-centered and carbon-centered PFRs are possible that can significantly affect their environmental and biological reactivity.
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Affiliation(s)
- Barry Dellinger
- Department of Chemistry, Louisiana State University, 413 Choppin Hall, Baton Rouge, LA 70803, USA
| | - Slawomir Lomnicki
- Department of Chemistry, Louisiana State University, 413 Choppin Hall, Baton Rouge, LA 70803, USA
| | - Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, 413 Choppin Hall, Baton Rouge, LA 70803, USA
| | - Zofia Maskos
- Department of Chemistry, Louisiana State University, 413 Choppin Hall, Baton Rouge, LA 70803, USA
| | - Randall W. Hall
- Department of Chemistry, Louisiana State University, 413 Choppin Hall, Baton Rouge, LA 70803, USA
| | - Julien Adounkpe
- Department of Chemistry, Louisiana State University, 413 Choppin Hall, Baton Rouge, LA 70803, USA
| | - Cheri McFerrin
- Department of Chemistry, Louisiana State University, 413 Choppin Hall, Baton Rouge, LA 70803, USA
| | - Hieu Truong
- Department of Chemistry, Louisiana State University, 413 Choppin Hall, Baton Rouge, LA 70803, USA
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Khachatryan L, Adounkpe J, Maskos Z, Dellinger B. Formation of cyclopentadienyl radical from the gas-phase pyrolysis of hydroquinone, catechol, and phenol. Environ Sci Technol 2006; 40:5071-6. [PMID: 16955909 DOI: 10.1021/es051878z] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The formation of radicals from the gas-phase pyrolysis of hydroquinone, catechol, and phenol over a temperature range of 400-750 degrees C was studied using the technique of low-temperature matrix isolation electron paramagnetic resonance (LTMI EPR). Cooling the reactor effluent from pyrolysis in a nitrogen carrier gas to 77 K produces a cryogenic matrix that exhibits poorly resolved EPR spectra. However, using carbon dioxide as a carrier gas formed a matrix that, upon annealing by slowly raising the matrix temperature followed by rapid recooling to 77 K, yielded more resolved, identifiable spectra. Annealed spectra of all three samples resulted in the generation of EPR spectra above 700 degrees C with 6 lines, hyperfine splitting constant approximately 6.0 G, and peak to peak width approximately 3 G that was readily assignable, based on comparison to the literature and theoretical calculations, as that of cyclopentadienyl radical. Pyrolysis at temperatures below 700 degrees C generated a carbon dioxide matrix isolation spectrum with a high g-value (>2.0040) that is attributed to oxygen-containing radicals such as semiquinone or phenoxyl. Conclusive identification of anticipated semiquinone, phenoxyl, and hydroxycyclopentadienyl radicals was complicated by the ability of these radicals to exist in carbon-centered and oxygen-centered resonance structures that can give different EPR spectra.
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Asatryan R, Davtyan A, Khachatryan L, Dellinger B. Molecular Modeling Studies of the Reactions of Phenoxy Radical Dimers: Pathways To Dibenzofurans. J Phys Chem A 2005; 109:11198-205. [PMID: 16331903 DOI: 10.1021/jp053047l] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The B3LYP hybrid density functional computational technique was applied to describe the sequence of phenoxy radicals coupling reactions leading to the formation of dibenzofurans. Reaction kinetic parameters were estimated for key reactions. Aromatization of bis-keto dimers of phenoxy radicals followed by intermediate dehydration or dehydroxylation was demonstrated to be a strongly stereoselective process. While the S,S-diastereomer of the ortho-C//ortho-C keto dimer forms (o,o')-dihydroxybiphenyl, a known dibenzofuran intermediate, via inter-ring hydrogen transfer reaction, the less stable R,S-stereoisomer can easily be transformed into another 5-hydroxyl-4,5-cyclohexadiene-2,3-benzofuran intermediate that provides an energetically more favorable pathway for formation of dibenzofuran. The possible channels of radical-chain processes that convert these intermediates to dibenzofuran and polychlorinated dibenzofurans are discussed.
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Affiliation(s)
- R Asatryan
- Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana, 70803, USA.
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Khachatryan L, Asatryan R, Dellinger B. An Elementary Reaction Kinetic Model of the Gas-Phase Formation of Polychlorinated Dibenzofurans from Chlorinated Phenols. J Phys Chem A 2004. [DOI: 10.1021/jp047762r] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Pharmaceutical and Toxicological Chemistry, Yerevan State Medical University, Yerevan 375025, Armenia
| | - Ruben Asatryan
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Pharmaceutical and Toxicological Chemistry, Yerevan State Medical University, Yerevan 375025, Armenia
| | - Barry Dellinger
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Pharmaceutical and Toxicological Chemistry, Yerevan State Medical University, Yerevan 375025, Armenia
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Abstract
The reactions of chlorine atoms and activated carbon have been studied over the temperature range of 200-400 degrees C using an isothermal flow reactor in conjunction with 337 nm laser photolysis of Cl2. These studies have shown that carbon tetrachloride is the major product, with chloroform, methylene chloride, and methyl chloride being formed in progressively decreasing yields. Trace quantities of methane, ethane, and dichloroethylenes were also observed. Mechanisms of carbon fragmentation by successive addition of chlorine atoms are proposed. The formation of small chlorinated hydrocarbons by the direct reaction of chlorine with carbon may be a key link in both the de novo and precursor pathways of formation of PCDD/F.
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Affiliation(s)
- Lavrent Khachatryan
- Department of Chemistry, Louisiana State University, Choppin Hall 413, Baton Rouge, LA 70803, USA
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Khachatryan L, Asatryan R, Dellinger B. Development of expanded and core kinetic models for the gas phase formation of dioxins from chlorinated phenols. Chemosphere 2003; 52:695-708. [PMID: 12738283 DOI: 10.1016/s0045-6535(03)00230-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Expanded, 45 reaction, and core, 12 reaction, kinetic models have been developed that account for the major features in the homogeneous formation of polychlorinated dibenzo-p-dioxins (PCDD) from the oxidation of 2,4,6-trichlorophenol (P). The expanded and core schemes provide good agreement between experimental and calculated yields of PCDDs using the CHEMKIN combustion package or the React kinetic program, respectively. Steady-state approximations of the reaction kinetic models including radical-molecule and radical-radical formation pathways of PCDD, as well as oxidative destruction pathways of chlorinated phenoxyl radicals, reveal a competition between reactions of chlorinated phenoxyl radicals with chlorinated phenols, recombination reactions of chlorinated phenoxyl mesomers, and destruction/decomposition of phenoxyl radicals.
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Affiliation(s)
- L Khachatryan
- Department of Chemistry, Louisiana State University, Choppin Hall 413, Baton Rouge, LA 70803, USA
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Asatryan RS, Mailyan NS, Khachatryan L, Dellinger B. Electronic elasticity-toxicity relationships for polychlorinated dibenzo-p-dioxin congeners. Chemosphere 2002; 48:227-236. [PMID: 12117058 DOI: 10.1016/s0045-6535(02)00065-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
SCF-MO computations have been performed on tetra- to octa-chlorinated dibenzo-p-dioxin congeners (PCDD) using an MNDO-PM3 Hamiltonian. Qualitative relationships were developed between empirical, international-toxic equivalence factors for PCDD congeners and their relative (specific) polarizabilities and mean values of second hyperpolarizabilities estimated using finite-field theory.
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Affiliation(s)
- Ruben S Asatryan
- Institute of Chemical Physics, Academy of Sciences of Armenia, Yerevan
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