Degradation Products Research Articles

Development of an accelerated ageing protocol for the study of phytocannabinoid stability in Cannabis sativa L.

Cannabis sativa L. is a plant belonging to the Cannabaceae family known primarily for its recreational use due to the psychoactive properties of Δ9-tetrahydrocannabinol (THC). Despite this, several compounds belonging to the category of phytocannabinoids have shown in recent years a number of potentially promising therapeutic effects that have increased the interest in the pharmaceutical field towards this plant. However, the content of these compounds is very variable and influenced by different factors, such as growing conditions and time of the year. An indication of the status and age of Cannabis samples is provided by the content of CBN, a minor phytocannabinoid and degradation product of other phytocannabinoids, including THC. In this research work an innovative, solid state analytical approach has been developed to observe and evaluate the variations in the content of two phytocannabinoids (CBN and CBD) in Cannabis-derived products over time. In order to simulate the ageing of the Cannabis samples, an artificially accelerated ageing procedure has been developed and optimised by using high temperatures. The analyses were carried out using an innovative ATR-FTIR method for solid state analysis, enabling direct analysis of a solid sample without any pretreatment phase. This study has allowed the development of an innovative analytical approach for the evaluation of the age and state of conservation of Cannabis samples and may be a useful tool both in the industrial, pharmaceutical and forensic fields.

Isolation, Identification, and Characterization of Forced Degradation Products of Bosentan by Using Advanced Analytical Techniques

ABSTRACTThe present study explains the degradation behavior of bosentan (BOS), active pharmaceutical ingredient (API) (BOS monohydrate), a Food and Drug Administration (FDA)–approved drug used for the treatment of chronic heart failure, subarachnoid hemorrhage, and Raynaud's syndrome pulmonary hypertension. The stress study was performed under various stress conditions such as acid hydrolysis, base hydrolysis, oxidation, thermal degradation, and photolysis as per International Council for Harmonization (ICH) guidelines and found three degradation products (DPs) under acid hydrolysis conditions (1 N HCl/4 h/60°C reflux conditions) (the net degradation of API ∼ 21.39%). The drug was found to be stable under the remaining conditions (thermal, photolytic, oxidative, and basic hydrolytic conditions). Mechanisms for forming the three acid DPs were also proposed and discussed. The DPs were initially detected by ultrahigh‐performance liquid chromatography–mass spectrometry analysis. These DPs were isolated by preparative HPLC and then characterized by high‐resolution mass spectrometry and nuclear magnetic resonance spectroscopy techniques. Based on the structural characterization study, all these DPs are new and not reported elsewhere in the literature to my knowledge. Many reports were found in the literature for the quantification of the drug in the APIs and formulation products. However, there is no report published yet for the identification and characterization of DPs of the BOS drug.

Prediction of Degradation Profiles for Various Sartans under Solvent-Free Mechanochemical Conditions.

For the approval of a drug, the stability data must be submitted to regulatory authorities. Such analyses are often time-consuming and cost-intensive. Forced degradation studies are mainly carried out under harsh conditions in the dissolved state, often leading to extraneous degradation profiles for a solid drug. Oxidative mechanochemical degradation offers the possibility of generating realistic degradation profiles. In this study, a sustainable mechanochemical procedure is presented for the degradation of five active pharmaceutical ingredients (APIs) from the sartan family: losartan potassium, irbesartan, valsartan, olmesartan medoxomil, and telmisartan. High-resolution mass spectrometry enabled the detection of impurities already present in untreated APIs and allowed the elucidation of degradation products. Significant degradation profiles could already be obtained after 15-60 min of ball milling time. Many of the identified degradation products are described in the literature and pharmacopoeias, emphasizing the significance of our results and the applicability of this approach to predict degradation profiles for drugs in the solid state.

Evaluation of atmospheric-plasma-source absorption mode Fourier transform Orbitrap mass spectrometry for chlorinated paraffin mixtures

Chlorinated paraffins (CP) are complex molecular mixtures occurring in a wide range of isomers and homologs of environmental hazards, whose analytical complexity demand advanced mass spectrometry (MS) methods for their characterization. The reported formation of chlorinated olefins (COs) and other transformation products during CP biotransformation and degradation can alter the MS analysis, increasing the high resolution required to distinguish CPs from their degradation products. An advanced setup hyphenating a plasma ionization source and an external high-performance data acquisition and processing system to the legacy hybrid LTQ Orbitrap XL mass spectrometer is reported. First, the study demonstrated the versatility of a liquid sampling atmospheric pressure glow discharge, as a soft ionization technique, for CP analysis. Second, enhanced resolution and sensitivity provided by the absorption mode Fourier transform spectral representation on this legacy mass spectrometer are shown. The developed Orbitrap-based platform allowed the detection of new isotopic clusters and CPs and COs to be distinguished at medium resolution (setting 30,000 at m/z 400, ~ 400 ms transients), and even chlorinated di-olefins (CdiOs) at higher resolution (setting 100,000 at m/z 400, ~ 1500 ms transients). Overall, such proof-of-principle instrumental improvements are promising for environmental and analytical research in the field of CP analysis.Graphical

Recovery of lithium from spent NMC batteries through water leaching, carbothermic reduction, and evaporative crystallization process

The demand for lithium grows exponentially due to its expanding range of applications. Because of their composition, spent lithium-ion batteries represent a promising secondary source of lithium. The present work focuses on a two-stage lithium recovery process applied to two different black masses from NMC 622 electric vehicle batteries after prior crushing and separation stages. In the first stage, hydrolysis is used to extract lithium compounds from the degradation products of the electrolyte (LiPF6). In the second stage, a carbothermic reduction process is carried out in which various reducing agents are evaluated. The result of this stage is a product that is leached with water and crystallised by evaporation. The result of the first stage is two industrially useful compounds: LiF, which is used in the production of lithium-ion battery electrolytes, and Li3PO4, which is used in the production of lithium-iron-phosphate batteries. In the second stage, Li2CO3 is recovered with a remarkably low LiF content, with a purity higher than 98.4 %. This process allows 90–94 % of the total lithium in the black mass to be recovered.

Synergistic activation of peroxymonosulfate by the laminate metals of MgMnFe-layered double hydroxides for imidacloprid degradation

Mg, Mn and Fe as environmental-friendly elements were introduced into the laminates of layered double hydroxides (LDHs) to synthesize MgMnFe-LDHs for peroxymonosulfate (PMS) activation to degrade imidacloprid (IMI). The catalytic activity of MgMnFe-LDHs was influenced by the Mn content in the LDH laminates, and Mg2Mn1Fe with Mn/Mg = 0.5 exhibited superior performance that 250 mg/L of dosage achieving 93.1 % degradation of IMI (10 mg/L) by activating PMS (0.65 mM) within 30 min. The mesoporous structure facilitated the contact between PMS and active sites, the abundant surface hydroxyl groups (–OH) provided sites for PMS complexation, and the synergism of Mn and Fe promoted PMS adsorption and electron transfer ability of Mg2Mn1Fe, thereby accelerating the production of SO4•− and •OH. The primary active sites were identified by density functional theory calculations that H-OI-OII-SO3- is absorbed through the binding of OI site with –OH of Mg2Mn1Fe, and the adsorption is more likely to occur on –OH connected with Mg-Mn-Fe rather than Mg-Mg-Fe and Mg-Mg-Mn. Based on the identification of degradation products, the degradation reaction types of IMI were proposed, including the opening of imidazole ring, carbonylation, denitrification, hydroxylation, dechlorination, and N-dealkylation. This study provides new insights into the design of efficient and environmentally-friendly LDH-based catalysts for PMS activation and the interaction mechanism between PMS and hydroxyl groups in LDH laminates.

Pollutant degradation and hydrogen production of landfill leachate membrane concentrates via aqueous phase reforming

Membrane filtration is a mainstream method for landfill leachate treatment, leaving the landfill leachate membrane concentrates (LLMCs) a high-toxicity residue. Conventional LLMCs disposal technology shows specific challenges due to the low biodegradability, high inorganic salts, and high heavy metal ions content of LLMCs. Therefore, it is necessary to degrade LLMCs with a more suitable technology. In this study, a special method was proposed to convert some organic chemicals into valuable compounds by aqueous phase reforming (APR). Ni-based catalysts (Ni//La2O3, Ni/CeO2, Ni/MgO, and Ni/Al2O3) were prepared to investigate the effect of different supports on the APR of LLMCs. APR performed outstanding characteristics in the decrease of chemical oxygen demand (COD) and total organic carbon (TOC), the degradation of macromolecules, and the removal of heavy metal ions in the aqueous phase. In addition, H2 was generated which is beneficial for energy compensating during the APR process. The best-performing catalyst (Ni/Al2O3) was selected to investigate the effects of reaction temperature, reaction time, and catalyst addition on product distribution. The optimal H2 selectivity (44.71%) and H2 production (11.63 mmol/g COD) were obtained at 250 °C with 2 g Ni/Al2O3 usage for 1 h. This paper provided a new perspective on the disposal of LLMCs, which will degrade pollutants efficiently.

Designing safe recycled high-density polyethylene (HDPE) for child toys

New high-density polyethylene (HDPE) manufactured from different percentage of post-consumer recycled HDPE milk bottles was studied through two static and dynamic migration tests using saliva simulant to assess the potential hazard to children. Sixty-nine compounds were identified, including several additives used in PE synthesis such as alkanes, alkenes, antioxidants and plasticizers as well as non-intentionally added substances (NIAS) like degradation products such as 2,6-di-tert-butyl-1,4-benzoquinone, 2,4-di-tert-butylphenol, phenol, 2,5-bis(1,1-dimethylethyl)-, 3,5-di-tert-butyl-4-hydroxybenzaldehyde, and 3,5-di-tert-butyl-4-hydroxyacetophenone, or various residues from flavoring agents, cleaning products and essential oils. Some of these compounds as the isomers p and o t-butylcyclohexyl acetate, 3-Octanol, 3,7-dimethyl- and thujanol acetate (3-) pose a potential risk to children, as their concentrations exceed the recommended Cramer values for high percentages of recycling. This suggests improving recycling processes by incorporating advanced cleaning to remove residual products and contaminants.

Degradation pathways and product formation mechanisms of asphaltene in supercritical water

Asphaltene is the compound with the most complex structure and the most difficult degradation in oily sludge, which is the key to limit the efficiency of supercritical water oxidation treatment of oily sludge. In this paper, the supercritical water oxidation process of asphaltene was investigated in terms of free radical reaction, degradation pathway, and product generation mechanism using ReaxFF molecular dynamics simulation method. The results showed that increasing temperature, increasing O2, and increasing H2O have different effects on HO2·generation. Benzene rings undergo fusion and condensation through hydrogenation abstraction and oxygen addition reactions, subsequently breaking down into long-chain alkanes. Increasing O2 can effectively promote the ring-opening of nitrogen-containing heterocycles. -COOH is the most important intermediate fragment for CO and CO2 generation, and there is a reaction competition with -CHO3 and -CO3. When the number of oxygen molecules increases from 300 to 700, the reaction frequency of -CHO3 and -CO3 to generate CO and CO2 increases by 17.14 % and 12.77 %·H2O determines the production of H2 by controlling the number of H·radicals present. As the amount of H2O increases from 500 to 1500, the product ratio of H2 increases from 12.73 % to 21.31 %. Environmental implicationAsphaltene is the most structurally complex organic matter in oily sludge, and its presence makes it difficult for oily sludge to be completely degraded by conventional treatment methods such as pyrolysis and incineration. Polycyclic aromatic hydrocarbons (PAHs) represented by asphaltene increase the carcinogenicity and mutagenicity of oily sludge, and even irreversibly pollute soil and groundwater. Supercritical water oxidation, as an efficient organic waste treatment technology, can realize harmlessness in a green and efficient way. So the study on the mechanism of supercritical water oxidation of asphaltene is of great significance for environmental protection.

Endolysin CHAP domain-carbosilane metallodendrimer complexes with triple action on Gram-negative bacteria: Membrane destabilization, reactive oxygen species production and peptidoglycan degradation

Bacterial resistance to antibiotics is a significant challenge that is associated with increased morbidity and mortality. Gram-negative bacteria are particularly problematic due to an outer membrane (OM). Current alternatives to antibiotics include antimicrobial peptides or proteins and multifunctional systems such as dendrimers. Antimicrobial proteins such as lysins can degrade the bacterial cell wall, whereas dendrimers can permeabilize the OM, enhancing the activity of endolysins against gram-negative bacteria. In this study, we present a three-stage action of endolysin combined with two different carbosilane (CBS) silver metallodendrimers, in which the periphery is modified with N-heterocyclic carbene (NHC) ligands coordinating a silver atom. The different NHC ligands contained hydrophobic methyl or N-donor pyridyl moieties. The effects of these endolysin/dendrimer combinations are based on OM permeabilization, peptidoglycan degradation, and reactive oxygen species production. The results showed that CBS possess a permeabilization effect (first action), significantly reduced bacterial growth at higher concentrations alone and in the presence of endolysin, increased ROS production (second action), and led to bacterial cell damage (third action). The complex formed between the CHAP domain of endolysin and a CBS silver metallodendrimer, with a triple mechanism of action, may represent an excellent alternative to other antimicrobials with only one resistance mechanism.

The influence of vermicompost on atrazine microbial degradation performance and pathway in black soil, Northeast China

The atrazine (ATR) is extensively used in dryland crops like corn and sorghum in black soil region of Northeast China, posing ecological risks due to toxic metabolites. Vermicompost are known for soil organic pollution remediation but their role in pesticide degradation in black soil remains understudied. The influence of vermicompost on the microbial degradation pathway of atrazine was assessed in this study. Although vermicompost didn't significantly boost atrazine removal, they notably aided in primary metabolite degradation, hydroxyatrazine (HYA), deisopropylatrazine (DIA), and deethylatrazine (DEA), reducing their content by 38.67 %. They also altered the soil microbial community structure, favoring atrazine-degrading bacteria like Proteobacteria, Firmicutes, and Actinobacteria. Five secondary degradation products were identified in vermicompost treatments. Atrazine degradation occurred via dechlorination, dealkylation, and deamination pathways mainly by Nocardioidacea, Streptomycetaceae, Bacillaceae, Sphingomonadaceae, Comamonadaceae and Nitrososphaeraceae. pH and available nitrogen (AN) influenced microbial community structure and atrazine degradation, correlating with vermicompost application rates. Future black soil remediation should optimize application rates based on atrazine content and soil properties.

Pesticide residues in European sediments: A significant concern for the aquatic systems?

The presence of pesticide residues in waterbed sediments poses a significant concern for aquatic ecosystems' health. This study examined pesticide contamination in sediments of 38 water bodies, embedded in agricultural-dominated regions, across eight European countries. Three indicators were targeted: occurrence, type, and concentrations of multiple pesticide residues in sediments. 196 pesticide residues (including degradation products) were tested in the sediment samples. The analytical results showed that only one sample was ‘pesticide-free’, three samples contained a single pesticide residue, and the remaining 34 samples contained mixtures of residues. Overall, 99 different residues were found in the sediments, with a maximum of 48 in a single sample. Twenty-seven out of the 99 detected residues were not approved for agricultural use at the time of sampling. The numbers of detected residues and pesticide levels varied among countries. AMPA, glyphosate and DDTs were the most common residues in sediment samples with frequencies of 76, 61, and 52%, respectively. The sediments from the Czech Republic had the highest pesticide concentrations, with total pesticide concentrations ranging between 600 and 1200 μg kg−1. The lowest total pesticide concentrations were found in Slovenia, Switzerland, Croatia, and Denmark, ranging between 80 and 120 μg kg−1. Sediments presented a mix of non-persistent and persistent compounds. Twelve of the detected pesticides are very persistent/stable in sediments, raising concerns about the long-term impacts of pesticides. Our study on the distribution of pesticide residues in European sediments provides valuable insights into the extent of pesticide contamination and possible risks of pesticides to water bodies' health. It also underlines the need for monitoring, research, and policy efforts to mitigate the impacts of pesticides, and to evaluate potential risks of re-use of dredged sediments.

Ferrate (VI) oxidation of sulfamethoxazole enhanced by magnetized sludge-based biochar: Active sites regulation and degradation mechanism analysis

Developing non radical systems for antibiotic degradation is crucial for addressing the inefficiency of conventional radical systems. In this study, novel magnetic-modified sludge biochar (MASBC) was synthesized to significantly enhance the oxidative degradation of sulfamethoxazole (SMX) by ferrate (Fe (VI)). In the Fe (VI)/MASBC system, 90.46% of SMX at a concentration of 10 μM and 49.34% of the total organic carbon (TOC) could be removed under optimal conditions of 100 μM of Fe (VI) and 0.40 g/L of MASBC within 10 min. Furthermore, the Fe (VI)/MASBC system was demonstrated with broad-spectrum removal capability towards sulfonamides in single or mixture. Quenching experiments, EPR analyses, and electrochemical experiments revealed that direct electron transfer (DET) and •O2− were mainly responsible for the removal of SMX, with functional groups (e.g., -OH, C=O) and Fe-O (redox of Fe (III)/Fe (II)) acting as the active sites, while the probe experiments showed that Fe (IV)/Fe (V) made a minor contribution to the degradation of SMX. Benefiting from the DET, the Fe (VI)/MASBC system exhibited a wide pH adaptation range (e.g., from 5.0 to 10.0) and strong anti-interference ability. The N atoms and their neighboring atoms in SMX were the prior degradation sites, with the cleavage of bond and ring opening. The degradation products showed low or non-toxicity according to ECOSAR program assessment. The removal of SMX remained within a reasonable range of 71.33%–90.46% over five consecutive cycles. Also, the Fe (VI)/MASBC system was demonstrated to be effectively applied for successful SMX removal in various water matrices, including ultrapure water, tap water, lake water, Yangtze River water, and wastewater. Therefore, this study offered new insights into the mechanism of Fe (VI) oxidation and would contribute to the efficient treatment of organic pollutants.

Electrodeposition of WO3 Nanoparticles Onto a Carbon Membrane Surface for the Development of a Hybrid Filtration/Photocatalysis System

This study proposes the development of a photoactive filtration membrane using carbon fiber (CF) modified with an n-type semiconductor (WO3) to create a hybrid filtration/photocatalysis system applied in water treatment for simultaneous retention and degradation of the emerging contaminant (Sertraline - SER). The membrane was prepared through chemical electrodeposition in a three-electrode electrochemical cell, utilizing CF as the working electrode, two-dimensionally stable anode counter electrodes (De Nora), and an Ag/AgCl 4.0 mol L-1 KCl reference electrode. The preparation conditions included: 5.0 mmol L-1 of Na2WO4, 0.075% (v/v) H2O2, pH 1.4, with a potential of -0.5 V applied for 1 h, followed by heat treatment at 450 °C.Characterizations revealed a mesoporous structure, with UV-Vis absorption (300 - 700 nm), a band gap of 3.6 eV, and a BET surface area of 3.1 m2 g-1. Micrographs illustrated the formation of a uniform layer of WO3 on the CF surface, and characteristic peaks of C and WO3 in the monoclinic phase were confirmed. XPS analysis assigned species, including C 1s, O 1s, W (4f, 4f7/2, 4d5/2 4d3/2), with an intense peak at 530 eV related to the metallic bond (W-O).The optimized experimental conditions: SER 2.0 mg L-1, volume 100 mL, flow rate 180 mL min-1, pH 5.6, UV LED irradiation, complete removal of SER was observed in 30 min when applied to real effluents from a water treatment plant before and after the chlorination step. Additionally, complete degradation was achieved after 90 min of the experiment in simulated effluents in Milli-Q water. The photoactive membrane proved effective under various conditions, achieving 1.41 mg L-1 SER degradation after five reuse cycles and complete SER degradation after 40 min under solar irradiation. Experiments with scavenger agents confirmed the participation of species (HO•, O2 •-, 1O2, h+, and H2O2) in the degradation process. Additionally, six degradation products were identified with mass-charge (m/z) of 176, 189, 191, 273, 293, and 322, generated from hydroxylation, demethylation, and dechlorination reactions.The photoactive membrane has shown excellent potential for applications in filtration processes, mitigating issues associated with fouling. It facilitates the rapid removal and effective degradation of pollutants while also allowing for its application under various irradiation conditions. This feature simplifies and enables effective management in the treatment of contaminated waters.

Characterization of Degradation Mechanisms of Alternative Electrolytes Solutions in Fast Charging Li-Ion Batteries

While the idea that fast charging batteries could be utilized in electric vehicles is enticing, current fast charging batteries face significant challenges that must be mitigated before this application is realized. Fast charging batteries currently suffer from capacity loss and degradation over time which not only affects battery life but poses a safety hazard. The current electrolyte, 1.2 M LiPF6 in 3:7 wt.% EC/EMC (Gen2), contains the salt LiPF6 that when exposed to moisture can form dangerous hydrofluoric acid and contains a carbonate-based solvent that when exposed to oxygen can ignite. In addition, batteries experience degradation over many cycles of fast charging which results in capacity fade and poor battery performance. However, previous studies have shown the potential for other electrolyte systems to mitigate these problems, specifically by using highly concentrated electrolytes1. These studies claim that using these electrolytes results in the formation of a solid electrolyte interphase (SEI) that passivates Li ions better than the Gen2 electrolyte. The SEI is a layer that forms on the anode within the battery and serves as a protective layer that allows for Li intercalation into graphite and can therefore protect against degradation. By using different electrolytes, a different SEI is formed, and different degradation mechanisms are observed. In this way, the SEI can be tuned to improve Li passivation and ionic conductivity by changing the electrolyte’s composition and concentration2. This research focuses on such alternative electrolyte systems and aims to characterize the different degradation mechanisms corresponding to each electrolyte. Favorable performance has been observed using 1.2 M LiFSI in 3:7 wt.% EC/EMC as an electrolyte. We are studying LiFSI in acetonitrile (AN) at higher concentrations than traditional Gen2 to quantify the SEI. We expect AN to form an anion derived SEI, a composition of which results in improved passivation of Li ions1. In this study, we characterize degradation of alternative electrolyte systems through x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Through these methods we can observe and quantify both crystalline, amorphous degradation products due to loss of Li inventory and loss of active material. XPS allows quantification of compositional changes in the SEI layer at the surface of the electrode. The SEM provides qualitative information on degradation such as visualizing lithium plating and dendrite formation. We implement quantitative XRD to measure the crystalline phases of the graphite anode, showing the degree of lithium intercalation and further quantifying degradation such as Li plating. Putting the results of these three characterization techniques together in tandem with electrochemical cycling data paints a picture of the degradation that happens on the anode of a fast-charging lithium-ion battery with respect to electrolyte composition.[1] Yamada, Y., Wang, J., Ko, S., Watanabe, E., & Yamada, A. (2019). Advances and issues in developing salt-concentrated battery electrolytes. Nature Energy. [2] Logan, E. R., & Dahn, J. R. (2020). Electrolyte Design for Fast-Charging Li-ion Batteries. Trends in Chemistry.

Open Circuit Voltage Hold Induced Degradation Under Dry Conditions and Recovery Strategies in PEMFC Electrodes

With regards to the decarbonization of the transportation sector in the near future, the importance of proton exchange membrane (PEM) fuel cells is shifting more and more from light-duty vehicles to heavy-duty vehicles, as well as to an application for maritime and aviation applications. With this change in the field of application, the requirements of the fuel cell system need to be adjusted towards an increased fuel efficiency and lifetime.1 Especially the targeted durability of 25,000 h for heavy-duty vehicles requires a detailed understanding of the degradation processes within the stack to be able to minimize performance losses or possible failure of the components.2 During the life cycle of a fuel cell electric vehicle, the stack encounters operation under increased temperature as well as under low relative humidity (RH). Both conditions are well known to lead to a degradation of the membrane electrode assembly (MEA).3,4 Deliberate operation under those conditions and at open circuit voltage (OCV) is commonly used to study the chemical degradation of the membrane. Here it is believed that gas crossover can lead to the formation of radicals, which attack the perfluoro sulfonic acid based ionomer chains and result in a variety of degradation products.5,6 Especially sulfonate group containing degradation species strongly adsorb on the Pt surface and reduce the oxygen reduction reaction (ORR) activity of the cathode catalyst. It was already shown that a suitable recovery step can restore of most of the observed performance losses.3,5 This work focusses on the chemical degradation and subsequent recovery strategies of a commercial MEA with an active area of 5 cm2 and a cathode loading of 0.4 mgPt/cm2. Although it is known that radical scavengers, like Ce3+ cations, minimize the chemical degradation within the membrane, we decided to use an MEA with a non-mitigated membrane (i.e., free of radical scavengers) in order to facilitate the degradation processes.5 As seen in the upper panel of Figure 1, the applied OCV hold for 72 h under H2/air (1000/1000 nccm) at 95 °C and at 30 % RH induces a voltage loss of ~115 mV (at 2.5 A/cm²) in the polarization curve after this accelerated stress test (AST), i.e., at end-of-degradation (EOD; red line/symbols), compared to the initial MEA performance at beginning-of-test (BOT; black line/symbols). In order to distinguish between reversible and irreversible losses, a subsequent recovery step at fully humidified conditions is implemented. The polarization curve at end-of-test (EOT; green line/symbols), i.e., after the recovery step, reveals that the majority of the observed losses is reversible. Provided that the applied recovery step accounts for all reversible effects, the remaining losses of ~45 mV (at 2.5 A/cm²) are of irreversible nature. On the one hand, those irreversible losses partially arise from a small increase in the high frequency resistance (HFR), which rises during the degradation period by ~2 mΩcm² (lower panel of Figure 1. On the other hand, the electrochemically active surface area (ECSA) is reduced by ~20 % over the course of the experiment, which leads to another unavoidable loss in performance. The comparison of the catalyst’s specific activity in units of mA/cm2 Pt, hence, accounting for the loss in ECSA, strongly suggests that the Pt surface at EOT approaches the initial state at BOT, which indicates a reversible degradation mechanism. References A. Cullen, K. C. Neyerlin, R. K. Ahluwalia, R. Mukundan, K. L. More, R. L. Borup, A. Z. Weber, D. J. Myers and A. Kusoglu, Nat. Energy, 6(5), 462–474 (2021).Marcinkoski, R. Vijayagopal, J. Adams, B. James, J. Kopasz, R. Ahluwalia, Hydrogen Class 8 Long Haul Truck Targets, DOE Hydrogen Program Record# 19006, https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf (2019).Du, T. A. Dao, P. V. J. Peitl, A. Bauer, K. Preuss, A. M. Bonastre, J. Sharman, G. Spikes, M. Perchthaler, T. J. Schmidt and A. Orfanidi, J. Electrochem. Soc., 167(14), 144513 (2020).Jomori, K. Komatsubara, N. Nonoyama, M. Kato and T. Yoshida, J. Electrochem. Soc., 160(9), F1067–F1073 (2013).Zhang, B. A. Litteer, F. D. Coms, R. Makharia, J. Electrochem. Soc., 159(7), F287–F293 (2012).A. Yandrasits, S. Marimannikkuppam, M. J. Lindell, K. A. Kalstabakken, M. Kurkowski and P. Ha, J. Electrochem. Soc., 169(3), 34526 (2022). Acknowledgements We gratefully acknowledge funding from the German Federal Ministry for Digital and Transport (BMDV) under the funding scheme H2Sky (funding code 03B10706). Figure 1

Comparative analysis of additive decomposition using one-dimensional and two–dimensional gas chromatography: Part II - Irgafos 168 and zinc stearate

Plastic production has experienced a significant increase in the last sixty years due to its cost-efficiency and adaptable characteristics, leading to the extensive use of additives to improve its performance and longevity. Due to the high demand for plastic, plastic waste production has increased, contaminating the environment and living beings by leaching additives, among other substances. Pyrolysis stands out among recycling techniques because it can handle mixed polymer waste feedstock. However, understanding the pyrolyzates distribution of additives is fundamental to assessing pyrolysis process of plastic waste. This study investigated the pyrolysis product distributions of two commonly used antioxidants, namely, Irgafos 168 and zinc stearate (ZnSt), using one-dimensional gas chromatography equipped with a quadruple mass spectrometer (GC–MS) and two-dimensional gas chromatography coupled to flame ionization detector and time–of–flight mass spectrometer (GC×GC–FID/TOF–MS). While GC separation technique provided limited information on product distribution, GC×GC offered enhanced resolution and identification of the decomposition products. In the pyrolysis of Irgafos 168 at 550 °C, GC identified 18 products, while GC×GC identified 198 products, representing an increase of approximately 11-fold. Similarly, for ZnSt, GC identified 67 products, while GC×GC identified 434 products, representing a 6-fold increase. GC×GC identified decomposition products from 15 different chemical classes for Irgafos 168 and 16 chemical classes for ZnSt, compared to 4 and 11 chemical classes identified by GC, respectively. Phenols and their derivatives were the major chemical class in the decomposition products of Irgafos 168 with a yield of 9.51 wt.%. In contrast, olefinic products were the dominant ones for ZnSt, with a yield of 9.73 wt.%. The major decomposition product of Irgafos 168 and ZnSt was 2‑tert‑butyl‑methylphenol (C11H16O) and C6 olefin (C6H12) with yields of 3.88 wt.%, and 1.13 wt.%, respectively. Utilizing the GC×GC separation method improved the ability to identify decomposition products, which can ultimately lead to a better understanding of antioxidant degradation that occurs during the pyrolysis process. GC×GC also provided thorough characterization of minor and co-eluted products along with major antioxidant degradation products. Additionally, the decomposition product distribution of Irgafos 168 and ZnSt was also compared with the primary antioxidants, Irganox 1010, Irganox 1076, and BHT, studied in part 1. The analysis indicated that the olefinic chemical class was the predominant one in Irganox 1010, Irganox 1076, and ZnSt, while ketones were the major chemical class in the decomposition of BHT and phenolics had the highest yield in Irgafos 168.

Evaluation of tetrachloroethylene (PCE) and its degradation products in human exhaled breath and indoor air in a community setting

Tetrachloroethylene (PCE) is a widely utilized volatile chemical in industrial applications, including dry cleaning and metal degreasing. Exposure to PCE potentially presents a significant health risk to workers as well as communities near contamination sites. Adverse health effects arise not only from PCE, but also from PCE degradation products, such as trichloroethylene (TCE) and vinyl chloride (VC). PCE, TCE, and VC can contaminate water, soil, and air, leading to exposure through multiple pathways, including inhalation, ingestion, and dermal contact. This study focused on a community setting in Martinsville, Indiana, a working-class Midwestern community in the United States, where extensive PCE contamination has occurred due to multiple contamination sites (referring to 'plumes'), including a Superfund site. Utilizing proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS), PCE, TCE, and VC concentrations were measured in the exhaled breath of 73 residents from both within and outside the plume areas. PCE was detected in 66 samples, TCE in 26 samples, and VC in 68 samples. Our results revealed a significant positive correlation between the concentrations of these compounds in exhaled breath and indoor air (Pearson correlation coefficients: PCE = 0.75, TCE = 0.71, and VC = 0.89). This study confirms the presence of PCE and its degradation products in exhaled breath in a community exposure investigation, demonstrating the potential of using exhaled breath analysis in monitoring exposure to environmental contaminants. This study showed the feasibility of utilizing PTR-TOF-MS in community investigations to assess exposure to PCE and its degradation products by measuring these compounds in exhaled breath and indoor air.

Catalytic activity of violet phosphorus-based nanosystems and the role of metabolites in tumor therapy.

Although nanocatalytic medicine has demonstrated its advantages in tumor therapy, the outcomes heavily relie on substrate concentration and the metabolic pathways are still indistinct. We discover that violet phosphorus quantum dots (VPQDs) can catalyze the production of reactive oxygen species(ROS) without requiring external stimuli and the catalytic substrates are confirmed to be oxygen (O2) and hydrogen peroxide (H2O2) through the computational simulation and experiments. Considering the short of O2 and H2O2 at the tumor site, we utilize calcium peroxide (CaO2) to supply catalytic substrates for VPQDs and construct nanoparticles together with them, named VPCaNPs. VPCaNPs can induce oxidative stress in tumor cells, particularly characterized by a significant increase in hydroxyl radicals and superoxide radicals, which cause substantial damage to the structure and function of cells, ultimately leading to cell apoptosis. Intriguingly, O2 provided by CaO2 can degrade VPQDs slowly, and the degradation product, phosphate, as well as CaO2-generated calcium ions, can promote tumor calcification. Antitumor immune activation and less metastasis are also observed in VPCaNPs administrated animals. In conclusion, our study unveils the anti-tumor activity of VPQDs as catalysts for generating cytotoxic ROS and the degradation products can promote tumor calcification, providing a promising strategy for treating tumors.

Mapping Photogenerated Electron-Hole Behavior of Graphene Oxide: Insight into a New Mechanism of Photosensitive Pollutant Degradation.

The use of graphene oxide (GO) photogenerated electron-hole (e-h+) pairs to degrade pollutants is a novel green method for wastewater treatment. However, the interaction between photosensitive pollutants and a GO-light system remains unclear. In this work, the mechanism of degradation of photosensitive pollutant tetracycline (TC) promoted by GO photogenerated e-h+ pairs was studied. Our studies encompassed the determination of TC removal kinetics, analysis of active substances for TC degradation, identification of degradation products, and computational modeling. Clear evidence shows that a new reaction mechanism of enhanced adsorption and induced generation of reactive oxygen species (ROS) was involved. This mechanism was conducive to significantly enhanced TC removal. Kinetic studies showed a first-order behavior that can be well described by the Langmuir-Hinshelwood model. Radical scavenging experiments confirmed that 1O2, •O2-, and holes (h+) were the main active substances for TC degradation. Electron spin resonance analysis indicated that photoexcited TC molecules may transfer electrons to the conduction band of GO to induce the generation of additional ROS. A major transformation product (m/z 459) during TC degradation was identified with liquid chromatography-mass spectrometry. Density functional theory calculation indicated a stronger adsorption between TC and GO under photoirradiation. This mechanism of photo-enhanced adsorption and synergistic induced generation of ROS provides a new strategy for the removal of emerging pollutants in water. Overall, the new mechanism revealed in this work expands the knowledge of applying GO to wastewater treatment and is of great reference value for research in this field.