An Overview of Degradation Strategies for Amitriptyline

Antidepressant drugs play a crucial role in the treatment of mental health disorders, but their efficacy and safety can be compromised by drug degradation. Recent reports point to several drugs found in concentrations ranging from the limit of detection (LOD) to hundreds of ng/L in wastewater plants around the globe; hence, antidepressants can be considered emerging pollutants with potential consequences for human health and wellbeing. Understanding and implementing effective degradation strategies are essential not only to ensure the stability and potency of these medications but also for their safe disposal in line with current environment remediation goals. This review provides an overview of degradation pathways for amitriptyline, a typical tricyclic antidepressant drug, by exploring chemical routes such as oxidation, hydrolysis, and photodegradation. Connex issues such as stability-enhancing approaches through formulation and packaging considerations, regulatory guidelines, and quality control measures are also briefly noted. Specific case studies of amitriptyline degradation pathways forecast the future perspectives and challenges in this field, helping researchers and pharmaceutical manufacturers to provide guidelines for the most effective degradation pathways employed for minimal environmental impact.

Chemical Characterization of Red Wine Polymers and Their Interaction Affinity with Odorants

In order to characterize red wine polymers with regard to their binding properties to aroma compounds (odorants), a qualitative and quantitative analysis of chemical degradation products after different chemical treatments (thiolytic, acidic, and alkaline depolymerization) of high -molecular-weight (HMW) fractions of red wine was performed. Using 1H NMR, LC-ToF-MS, LC-MS/MS, and HPIC revealed key structural features such as carbohydrates, organic acids, phenolic compounds, anthocyanins, anthocyanidins, amino acids, and flavan-3-ols responsible for odorant-polymer interactions. Further, NMR-based interaction studies of the selected aroma compounds 3-methylbutanol, cis-whisky lactone, 3-methylbutanoic acid, and 3-isobutyl-2-methoxypyrazine with HMW polymers after chemical treatment demonstrated a reduced interaction affinity of the polymer compared to the native HMW fractions, and further, the importance of aromatic compounds such as flavan-3-ols for the formation of odorant polymer interactions. In addition, these observations could be verified by human sensory experiments. For the first time, the combination of a compositional analysis of red wine polymers and NMR-based interaction studies with chemically treated HMW fractions enabled the direct analysis of the correlation of the polymer's structure and its interaction affinity with key odorants in red wine.

Chromophores' Contribution to Color Changes of Thermally Modified Tropical Wood Species

This work examines the effect of thermal modification temperature (180, 200, and 220 °C) in comparison with reference (untreated) samples on selected optical properties of six tropical wood species-Sp. cedar (Cedrala odorata), iroko (Chlorophora excelsa), merbau (Intsia spp.), meranti (Shorea spp.), padouk (Pterocarpus soyauxii), and teak (Tectona grandis). The main goal is to expand the existing knowledge in the field of wood thermal modification by understanding the related degradation mechanisms associated with the formation of chromophoric structures and, above all, to focus on the change in the content of extractive substances. For solid wood, the CIELAB color space parameters (L*, a*, b*, and ΔE*), yellowness (Y), ISO brightness, and UV-Vis diffuse reflectance spectra were obtained. Subsequently, these wood samples were extracted into three individual solvents (acetone, ethanol, and ethanol-toluene). The yields of the extracted compounds, their absorption spectra, and again L*, a*, b*, ΔE*, and Yi parameters were determined. With increasing temperatures, the samples lose brightness and darken, while their total color difference grows (except merbau). The highest yield of extractives (mainly phenolic compounds, glycosides, and dyes) from thermally modified samples was usually obtained using ethanol. New types of extractives (e.g., 2-furaldehyde, lactones, formic acid, some monomer derivatives of phenols, etc.) are already created around a temperature of 180 °C and may undergo condensation reactions at higher temperatures. For padouk, merbau, teak, and partially iroko modified at temperatures of 200 and 220 °C, there was a detected similarity in the intensities of their UV-Vis DR spectra at the wavelength regions corresponding to phenolic aldehydes, unsaturated ketones, quinones, stilbenes, and other conjugated carbonyl structures. Overall, a statistical assessment using PCA sorted the samples into five clusters. Cluster 3 consists of almost all samples modified at 200 and 220 °C, and in the other four, the reference and thermally modified samples at 180 °C were distributed. The yellowness of wood (Y) has a very high dependence (r = 0.972) on its brightness (L*) and the yellowness index of the extractives in acetone Yi(Ac), whose relationship was described by the equation Y = -0.0951 × Y(Ac) + 23.3485.

Study of Aerogel-Modified Recycled Polyurethane Nanocomposites

In this study, a liquid regenerated polyether polyol was obtained after the degradation of waste PU foam by the two-component decrosslinker agents ethylene glycol and ethanolamine. The regenerated polyol-based polyurethane foam was modified by adding different ratios of SiO2 aerogel through the self-preparation of silica aerogel (SiO2 aerogel) to prepare aerogel/regenerated polyurethane foam nanocomposites of SiO2 aerogel-modified regenerated polyurethane composites. A series of analytical tests on self-prepared silica aerogel and aerogel-modified recycled polyurethane foam composites were performed. The analysis of the test results shows that the regenerated rigid PU foam obtained with SiO2 aerogel addition of 0.3% in the polyurethane degradation material has a small density, low thermal conductivity, and higher compressive strength; hence, the prepared silica aerogel-regenerated polyol-based polyurethane nanocomposite has good thermal insulation and strength support properties. The clean, low-carbon, and high-value utilization of recycled waste polyurethane was achieved.

Durability and Performance Analysis of Polymer Electrolyte Membranes for Hydrogen Fuel Cells by a Coupled Chemo-mechanical Constitutive Model and Experimental Validation

In this paper, a chemo-mechanically coupled behavior of Nafion 212 is investigated through predictive multiphysics modeling and experimental validation. Fuel cell performance and durability are critically determined by the mechanical and chemical degradation of a perfluorosulfonic acid (PFSA) membrane. However, how the degree of chemical decomposition affects the material constitutive behavior has not been clearly defined. To estimate the degradation level quantitatively, fluoride release is measured. The PFSA membrane in tensile testing shows nonlinear behavior, which is modeled by J₂ plasticity-based material modeling. The material parameters, which contain hardening parameters and Young's modulus, are characterized in terms of fluoride release levels by inverse analysis. In the sequel, membrane modeling is performed to investigate the life prediction due to humidity cycling. A continuum-based pinhole growth model is adopted in response to mechanical stress. As a result, validation is conducted in comparison with the accelerated stress test (AST) by correlating the size of the pinhole with the gas crossover generated in the membrane. This work provides a dataset of degraded membranes for performance and suggests the quantitative understanding and prediction of fuel cell durability with computational simulation.

The Effect of Chemical Degradation and Polishing on the Gloss of Composite Dental Materials

This aim of this study was to investigate surface gloss changes of different composite dental materials after chemical degradation or polishing. Five different composites were used (Evetric, GrandioSO, Admira Fusion, Filtek Z550, Dynamic Plus). The gloss of the tested material was measured with a glossmeter before and after chemical degradation in different acidic beverages. Statistical analysis was performed using a t-test for dependent samples, ANOVA, and a post hoc test. For comparison between groups, a level of significance was set at 0.05. Initial gloss values ranged from 51 to 93 at baseline to 32 to 81 after chemical degradation. The highest values were obtained for Dynamic Plus (93.5 GU) and GrandioSO (77.8 GU), followed by Admira Fusion (82 GU) and Filtek Z550 (70.5 GU). Evetric showed the lowest initial gloss values. After acidic exposures, the gloss measurements revealed different patterns of surface degradation. The results showed that the gloss of the samples decreased with time regardless of the treatment. The interaction between chemical-erosive beverages and the composite could lead to a decrease in the surface gloss of the composite restoration. The nanohybrid composite showed less gloss changes under acidic conditions, suggesting that it is more suitable for anterior restorations.

Glucosinolates, a natural chemical arsenal: More to tell than the myrosinase story

Glucosinolates are a group of thioglucosides that belong to the class of plant nitrogen-containing natural products. So far, very little biological activity has been associated with intact glucosinolates. The hydrolysis of glucosinolates has, for long, attracted attention because of the potent biological activity of the hydrolysis products. From allelopathic to antiparasitic, antimicrobial and antineoplastic effects, the activity spectrum of the degradation products of typical glucosinolates has been the subject of much research. The present review seeks to address the various means of glucosinolate degradation (thermal, enzymatic, or chemical degradation) and the ensuing products. It also aims to draw a comparative profile of the various antimicrobial effects of these degradation products to provide a further understanding of the biological function of these important compounds.

Learning Relationships Between Chemical and Physical Stability for Peptide Drug Development

PURPOSE OR OBJECTIVE

Chemical and physical stabilities are two key features considered in pharmaceutical development. Chemical stability is typically reported as a combination of potency and degradation product. Moreover, fluorescent reporter Thioflavin-T is commonly used to measure physical stability. Executing stability studies is a lengthy process and requires extensive resources. To reduce the resources and shorten the process for stability studies during the development of a drug product, we introduce a machine learning-based model for predicting the chemical stability over time using both formulation conditions as well as aggregation curves.

METHODS

In this work, we develop the relationships between the formulation, stability timepoint, and the chemical stability measurements and evaluated the performance on a random test set. We have developed a multilayer perceptron (MLP) for total degradation prediction and a random forest (RF) model for potency.

RESULTS

The coefficient of determination (R²) of 0.945 and a mean absolute error (MAE) of 0.421 were achieved on the test set when using MLP for total degradation. Similarly, we achieved a R² of 0.908 and MAE of 1.435 when predicting potency using the RF model. When physical stability measurements are included into the MLP model, the MAE of predicting TD decreases to 0.148. Using a similar strategy for potency prediction, the MAE decreases to 0.705 for the RF model.

CONCLUSIONS

We conclude two important points: first, chemical stability can be modeled using machine learning techniques and second there is a relationship between the physical stability of a peptide and its chemical stability.

Flame-Retardant Cycloaliphatic Epoxy Systems with High Dielectric Performance for Electronic Packaging Materials

Flame-retardant cycloaliphatic epoxy systems have long been studied; however, the research suffers from slow and unsatisfactory advances. In this work, we synthesized a kind of phosphorus-containing difunctional cycloaliphatic epoxide (called BCEP). Then, triglycidyl isocyanurate (TGIC) was mixed with BCEP to achieve epoxy systems that are rich in phosphorus and nitrogen elements, which were cured with 4-methylhexahydrobenzene anhydride (MeHHPA) to obtain a series of flame-retardant epoxy resins. Curing behaviors, flame retardancy, thermal behaviors, dielectric performance, and the chemical degradation behaviors of the cured epoxy system were investigated. BCEP-TGIC systems showed a high curing activity, and they can be efficiently cured, in which the incorporation of TGIC decreased the curing activity of the resin. As the ratio of BCEP and TGIC was 1:3, the cured resin (BCEP₁-TGIC₃) showed a relatively good flame retardancy with a limiting oxygen index value of 25.2%. In the cone calorimeter test, they presented a longer time to ignition and a lower heat release than the commercially available cycloaliphatic epoxy resins (ERL-4221). BCEP-TGIC systems presented good thermal stability, as the addition of TGIC delayed the thermal weight loss of the resin. BCEP₁-TGIC₃ had high dielectric performance and outperformed ERL-4221 over a frequency range of 1 HZ to 1 MHz. BCEP₁-TGIC₃ could achieve degradation under mild conditions in an alkali methanol/water solution. Benefiting from the advances, BCEP-TGIC systems have potential applications as electronic packaging materials in electrical and electronic fields.

Alkaline Stability of Anion-Exchange Membranes

Recently, the development of durable anion-exchange membrane fuel cells (AEMFCs) has increased in intensity due to their potential to use low-cost, sustainable components. However, the decomposition of the quaternary ammonium (QA) cationic groups in the anion-exchange membranes (AEMs) during cell operation is still a major challenge. Many different QA types and functionalized polymers have been proposed that achieve high AEM stabilities in strongly alkaline aqueous solutions. We previously developed an ex situ technique to measure AEM alkaline stabilities in an environment that simulates the low-hydration conditions in an operating AEMFC. However, this method required the AEMs to be soluble in DMSO solvent, so decomposition could be monitored using ¹H nuclear magnetic resonance (NMR). We now report the extension of this ex situ protocol to spectroscopically measure the alkaline stability of insoluble AEMs. The stability ofradiation-grafted (RG) poly(ethylene-co-tetrafluoroethylene)-(ETFE)-based poly(vinylbenzyltrimethylammonium) (ETFE-TMA) and poly(vinylbenzyltriethylammonium) (ETFE-TEA) AEMs were studied using Raman spectroscopy alongside changes in their true OH^- conductivities and ion-exchange capacities (IEC). A crosslinked polymer made from poly(styrene-co-vinylbenzyl chloride) random copolymer and N,N,N',N'-tetraethyl-1,3-propanediamine (TEPDA) was also studied. The results are consistent with our previous studies based on QA-type model small molecules and soluble poly(2,6-dimethylphenylene oxide) (PPO) polymers. Our work presents a reliable ex situ technique to measure the true alkaline stability of AEMs for fuel cells and water electrolyzers.

Bitumen Aging-Laboratory Simulation Methods Used in Practice and Selected Directions of Research on New Methods

Changes in the properties of bitumen binders that occur as a result of aging have a huge impact on the durability of products produced from them. In particular, asphalt pavements, which constitute the most common use of petroleum bitumen, are susceptible to damage resulting from the increasing stiffness of the bitumen during its life cycle. Increased stiffness of asphalt pavements reduces the pavement resistance to low-temperature cracks and fatigue cracks, ultimately leading to the loss of their functional properties and the need for road repair. The rate of changes in bitumen properties is influenced by many factors, the most important of which are environmental conditions, technological parameters of binder processing, and physicochemical properties. The greatest impact on minimizing the adverse effect of aging is the use of bitumen suitably resistant to aging, and changing the technological parameters of its application. This article reviews the literature and standardized test methods of bitumen aging, with a focus on the methods that are most often used in practice, to evaluate the suitability of bitumen for use in road construction. The presented methods are limited to aging simulation. This mini-review presents the most important stages of aging procedures, their advantages and limitations, as identified by the authors of this publication for different types of bitumen. Moreover, the most important directions of developments in the field of new laboratory aging tests are highlighted. The suggestions are based on the industrial practice of the authors of this review, taking into account identified demands for quality control in the industry.

The Characterization of Titanium Particles Released from Bone-Level Titanium Dental Implants: Effect of the Size of Particles on the Ion Release and Cytotoxicity Behaviour

Many studies are being carried out on the particles released during the implantoplasty process in the machining of dental implants to remove bacterial biofilms. However, there are no studies on the release of particles produced by the insertion of bone-level dental implants due to the high compressive frictional loads between the rough titanium implant and the bone tissue. This paper aims to characterize the released particles and determine the release of titanium ions into the physiological environment and their cytocompatibility. For this purpose, 90 dental implants with a neck diameter of 4 mm and a torque of 22 Ncm were placed in 7 fresh cow ribs. The placement was carried out according to the established protocols. The implants had a roughness Ra of 1.92 μm. The arrangement of the particles in the bone tissue was studied by micro-CT, and no particle clusters were observed. The different granulometries of 5, 15, and 30 μm were obtained; the specific surface area was determined by laser diffraction; the topography was determined by scanning electron microcopy; and the particles were chemically analysed by X-ray energy microanalysis. The residual stresses of the particles were obtained by X-ray diffraction using the Bragg-Bentano configuration. The release of titanium ions to the physiological medium was performed using ICP-MS at 1, 3, 7, 14, and 21 days. The cytocompatibility of the particles with HFF-1 fibroblast and SAOS-2 osteoblast cultures was characterized. The results showed that the lowest specific surface area (0.2109 m²/g) corresponds to the particles larger than 30 μm being higher than 0.4969 and 0.4802 m²/g of those that are 5 and 15 μm, respectively, observing in all cases that the particles have irregular morphologies without contamination of the drills used in the surgery. The highest residual stresses were found for the small particles, -395 MPa for the 5 μm particles, and -369 for the 15 μm particles, and the lowest residual stresses were found for the 30 μm particles with values of -267 MPa. In all cases, the residual stresses were compressive. The lowest ion release was for the 30 μm samples, as they have the lowest specific surface area. Cytocompatibility studies showed that the particles are cytocompatible, but it is the smallest ones that are lower and very close to the 70% survival limit in both fibroblasts and osteoblasts.

Effects of Biological and Chemical Degradation on the Properties of Scots Pine Wood-Part I: Chemical Composition and Microstructure of the Cell Wall

Research on new conservation treatment for archaeological wood requires large amounts of wooden material. For this purpose, artificial wood degradation (biological-using brown-rot fungus Coniophora puteana, and chemical-using NaOH solution) under laboratory conditions was conducted to obtain an abundance of similar samples that mimic naturally degraded wood and can serve for comparative studies. However, knowledge about its properties is necessary to use this material for further study. In this study, the chemical composition and microstructure of degraded cell walls were investigated using FT-IR, XRD, helium pycnometry and nitrogen absorption methods. The results show that biological degradation caused the loss of hemicelluloses and celluloses, including the reduction in cellulose crystallinity, and led to lignin modification, while chemical degradation mainly depleted the amount of hemicelluloses and lignin, but also affected crystalline cellulose. These changes affected the cell wall microstructure, increasing both surface area and total pore volume. However, the chemical degradation produced a greater number of mesopores of smaller size compared to fungal decomposition. Both degradation processes weakened the cell wall's mechanical strength, resulting in high shrinkage of degraded wood during air-drying. The results of the study suggest that degraded wood obtained under laboratory conditions can be a useful material for studies on new consolidants for archaeological wood.

Engineering Multiscale Coupled Electron/Ion Transport in Battery Electrodes

Coupled electron/ion transport is a defining characteristic of electrochemical processes, for example, battery charge/discharge. Analytical models that represent the complex transport and electrochemical processes in an electrode in terms of equivalent electrical circuits provide a simple, but successful framework for understanding the kinetics of these coupled transport phenomena. The premise of this review is that the nature of the time-dependent phase transitions in dynamic electrochemical environments serves as an important design parameter, orthogonal to the intrinsic mixed conducting properties of the active materials in battery electrodes. A growing body of literature suggests that such phase transitions can produce divergent extrinsic resistances in a circuit model (e.g., R_e, describing electron transport from an active electrode material to the current collector of an electrode, and/or R_ion, describing ion transport from a bulk electrolyte to the active material surface). It is found that extrinsic resistances of this type play a determinant role in both the electrochemical performance and long-term stability of most battery electrodes. Additionally, successful suppression of the tendency of extrinsic resistances to accumulate over time is a requirement for practical rechargeable batteries and an important target for rational design. We highlight the need for battery electrode and cell designs, which explicitly address the specific nature of the structural phase transition in active materials, and for advanced fabrication techniques that enable precise manipulations of matter at multiple length scales: (i) meso-to-macroscopic conductive frameworks that provide contiguous electronic/ion pathways; (ii) nanoscale uniform interphases formed on active materials; and (iii) molecular-level structures that promote fast electron and/or ion conduction and mechanical resilience.

The Impact of Glycerol on an Affibody Conformation and Its Correlation to Chemical Degradation

The addition of glycerol to protein solutions is often used to hinder the aggregation and denaturation of proteins. However, it is not a generalised practice against chemical degradation reactions. The chemical degradation of proteins, such as deamidation and isomerisation, is an important deteriorative mechanism that leads to a loss of functionality of pharmaceutical proteins. Here, the influence of glycerol on the chemical degradation of a protein and its correlation to glycerol-induced conformational changes is presented. The time-dependent chemical degradation of a pharmaceutical protein, GA-Z, in the absence and presence of glycerol was investigated in a stability study. The effect of glycerol on protein conformation and oligomerisation was characterised using asymmetric field-flow fractionation and small-angle neutron scattering in a wide glycerol concentration range of 0–90% v/v. The results from the stability study were connected to the observed glycerol-induced conformational changes in the protein. A correlation between protein conformation and the protective effect of glycerol against the degradation reactions deamidation, isomerisation, and hydrolysis was found. The study reveals that glycerol induces conformational changes of the protein, which favour a more compact and chemically stable state. It is also shown that the conformation can be changed by other system properties, e.g., protein concentration, leading to increased chemical stability.

Polydopamine Coated CeO2 as Radical Scavenger Filler for Aquivion Membranes with High Proton Conductivity

CeO₂ nanoparticles were coated with polydopamine (PDA) by dopamine polymerization in water dispersions of CeO₂ and characterized by Infrared and Near Edge X-ray Absorption Fine Structure spectroscopy, Transmission Electron Microscopy, Thermogravimetric analysis and X-ray diffraction. The resulting materials (PDAx@CeO₂, with x = PDA wt% = 10, 25, 50) were employed as fillers of composite proton exchange membranes with Aquivion 830 as ionomer, to reduce the ionomer chemical degradation due to hydroxyl and hydroperoxyl radicals. Membranes, loaded with 3 and 5 wt% PDAx@CeO₂, were prepared by solution casting and characterized by conductivity measurements at 80 and 110 °C, with relative humidity ranging from 50 to 90%, by accelerated ex situ degradation tests with the Fenton reagent, as well as by in situ open circuit voltage stress tests. In comparison with bare CeO₂, the PDA coated filler mitigates the conductivity drop occurring at increasing CeO₂ loading especially at 110 °C and 50% relative humidity but does not alter the radical scavenger efficiency of bare CeO₂ for loadings up to 4 wt%. Fluoride emission rate data arising from the composite membrane degradation are in agreement with the corresponding changes in membrane mass and conductivity.

The Impact of Chemical-Mechanical Ex Situ Aging on PFSA Membranes for Fuel Cells

A proton-exchange membrane fuel cell (PEMFC) constitutes today one of the preferred technologies to promote hydrogen-based alternative energies. However, the large-scale deployment of PEMFCs is still hampered by insufficient durability and reliability. In particular, the degradation of the polyelectrolyte membrane, caused by harsh mechanical and chemical stresses experienced during fuel cell operation, has been identified as one of the main factors restricting the PEMFC lifetime. An innovative chemical-mechanical ex situ aging device was developed to simultaneously expose the membrane to mechanical fatigue and an oxidizing environment (i.e., free radicals) in order to reproduce conditions close to those encountered in fuel cell systems. A cyclic compressive stress of 5 or 10 MPa was applied during several hours while a degrading solution (H₂O₂ or a Fenton solution) was circulated in contact with the membrane. The results demonstrated that both composite Nafion^™ XL and non-reinforced Nafion^™ NR211 membranes are significantly degraded by the conjoint mechanical and chemical stress exposure. The fluoride emission rate (FER) was generally slightly lower with XL than with NR211, which could be attributed to the degradation mitigation strategies developed for composite XL, except when the pressure level or the aging duration were increased, suggesting a limitation of the improved durability of XL.

Research Progress of Proton Exchange Membrane Failure and Mitigation Strategies

Proton exchange membrane (PEM) is critical for the efficient, reliable and safe operation of proton exchange membrane fuel cells (PEMFC). The lifetime of PEM is the main factor restricting the commercialization of PEMFC. The complexity of operating conditions, such as open-circuit/idling, dynamic load and startup-shutdown under automotive conditions, on PEMFC will cause the mechanical and chemical degradation of PEM and affect the service life of PEMFC. In order to understand the degradation behavior and durability of PEM, this paper presents an overview of the degradation failure mechanism and mitigation strategies of PEM. The mechanical and chemical degradation behavior of PEM and its causes, as well as the mitigation strategies are discussed in order to give a direction for PEM design and fuel cell system control strategy. It is proposed as a primary principle in order to further develop and promote the durability of PEM, to focus on the material improvement and system engineering.

Amorphization of Thiamine Chloride Hydrochloride: Effects of Physical State and Polymer Type on the Chemical Stability of Thiamine in Solid Dispersions

Thiamine is an essential micronutrient, but delivery of the vitamin in supplements or foods is challenging because it is unstable under heat, alkaline pH, and processing/storage conditions. Although distributed as a crystalline ingredient, thiamine chloride hydrochloride (TClHCl) likely exists in the amorphous state, specifically in supplements. Amorphous solids are generally less chemically stable than their crystalline counterparts, which is an unexplored area related to thiamine delivery. The objective of this study was to document thiamine degradation in the amorphous state. TClHCl:polymer dispersions were prepared by lyophilizing solutions containing TClHCl and amorphous polymers (pectin and PVP (poly[vinylpyrrolidone])). Samples were stored in controlled temperature (30–60 °C) and relative humidity (11%) environments for 8 weeks and monitored periodically by X-ray diffraction (to document physical state) and HPLC (to quantify degradation). Moisture sorption, glass transition temperature (T_g), intermolecular interactions, and pH were also determined. Thiamine was more labile in the amorphous state than the crystalline state and when present in lower proportions in amorphous polymer dispersions, despite increasing T_g values. Thiamine was more stable in pectin dispersions than PVP dispersions, attributed to differences in presence and extent of intermolecular interactions between TClHCl and pectin. The results of this study can be used to control thiamine degradation in food products and supplements to improve thiamine delivery and decrease rate of deficiency.

Polyurethane Recycling and Disposal: Methods and Prospects

Growing water and land pollution, the possibility of exhaustion of raw materials and resistance of plastics to physical and chemical factors results in increasing importance of synthetic polymers waste recycling, recovery and environmentally friendly ways of disposal. Polyurethanes (PU) are a family of versatile synthetic polymers with highly diverse applications. They are class of polymers derived from the condensation of polyisocyanates and polyalcohols. This paper reports the latest developments in the field of polyurethane disposal, recycling and recovery. Various methods tested and applied in recent years have proven that the processing of PU waste can be economically and ecologically beneficial. At the moment mechanical recycling and glycolysis are the most important ones. Polyurethanes’ biological degradation is highly promising for both post-consumer and postproduction waste. It can also be applied in bioremediation of water and soil contaminated with polyurethanes. Another possibility for biological methods is the synthesis of PU materials sensitive to biological degradation. In conclusion, a high diversity of polyurethane waste types and derivation results in demand for a wide range of methods of processing. Furthermore, already existing ones appear to be enough to state that the elimination of not reprocessed polyurethane waste in the future is possible.

Understanding Concomitant Physical and Chemical Transformations of Simvastatin During Dry Ball Milling

The present study investigates concomitant processes of solid-state disordering and oxidation of simvastatin during milling. The separate dry ball milling of crystalline and amorphous powders of simvastatin were conducted at ambient temperature for 10 and 60 min each. The relative crystallinity was determined using X-ray scattering and oxidative degradation was analyzed using liquid chromatography. The physical and chemical transformations in the milled powder were evaluated using modulated differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. The disordering during milling of the crystalline powder was found to progressively decrease the crystallinity. For the amorphous starting material, milling for 10 min induced a large extent of recrystallization, while milling for 60 min largely re-amorphized the powder. This solid-state disordering and/or ordering were accompanied by progressive air oxidation during milling. The infrared spectroscopic analysis revealed the molecular manifestations associated with the physicochemical transformations in the disordered solid states. The melting point of simvastatin depressed systematically with the increase in the degree of disorder as well as the degradation. The in situ cooling in DSC of milled samples from their molten state led to the formation of the co-amorphous phase between the drug and degradation products, which showed a consistent increase in glass transition temperature with the increase in the content of degradation products. The study overall demonstrates the solid-state re-ordering and disordering of crystalline and amorphous simvastatin accompanied by chemical degradation as the consequence of the mechano-activation.

[Characteristics of C2-C6 Hydrocarbons During the Winter Air Pollution Period in Beijing Urban Area]

A C2-C6 hydrocarbons monitoring campaign was carried out in the Beijing Southeastern Urban Area during December 2015. Twenty-five compounds excluding benzene were detected by an on-line VOCs analyzer; the sum of their concentrations is referred to as C2-C6 HCs in this study. During the monitoring period, C2-C6 HCs ranged from 12.4×10^-9 to 297.5×10^-9. The mean value of C2-C6 HCs reached 29.4×10^-9, 63.2×10^-9, 85.5×10^-9, 94.9×10^-9, and 131.8×10^-9, respectively, in AQ Ⅰ (air quality) (hourly PM_2.5<35 μg·m^-3), AQ Ⅱ (hourly PM_2.5:35-75 μg·m^-3), AQ Ⅲ (hourly PM_2.5:75-150 μg·m^-3), AQ Ⅳ (hourly PM_2.5:150-250 μg·m^-3), and AQ Ⅴ (hourly PM_2.5:>250 μg·m^-3). Moreover, the mole percentage of alkanes, alkenes, and ethyne significantly varied, 47% vs. 59%, 45% vs. 30%, and 7% vs. 12% (AQ I vs. AQ V). The diurnal variation of C2-C6 HCs presented two peaks at 08:00-09:00 and 17:00-18:00 not only in clean days (when 24-h PM_2.5<75 μg·m^-3) but also in polluted days (when 24-h PM_2.5>75 μg·m^-3). This result is consistent with the normal traffic pattern and indicates the significant impact of vehicle emissions on atmospheric hydrocarbon concentrations. Furthermore, we calculated the HCs/CO (×10^-9/×10^-6) ratio to prevent the impact of meteorological diffusion on C2-C6 HCs and to trace the physical transport process and the chemical degradation process of hydrocarbons. The C2-C6 HCs/CO ratio and the individual hydrocarbon to CO ratio presented a notable decreasing trend with worsening air quality, 90.6 (AQ Ⅰ), 63.8 (AQ Ⅱ), 56.9 (AQ Ⅲ), 37.4 (AQ Ⅳ), and 36.4 (AQ Ⅴ). However, the rate of decrease in the ratio of individual hydrocarbons to CO in the polluted period (AQ Ⅲ-Ⅴ) relative to the clean period (AQ I-Ⅱ) was never effectively related to the kinetic parameters of the reactions with the OH radical. Therefore, the strong chemical degradation of C2-C6 hydrocarbons in the polluted air was denied as the main reason. The HYSPLIT trajectory model showed that the transported air mass from the north and northwest and from the south and southwest prevail in the clean period and in the polluted period, respectively. Compared to the northern region, there were more sources of fossil fuel combustion in the southern region, which led to a lower HCs/CO ratio for the air mass in the southern region. Therefore, the increase in C2-C6 hydrocarbons during the polluted period was not only caused by the accumulation of local emissions but also by the air mass transport from the south.

Enhanced Long-term and Thermal Stability of Polymer Solar Cells in Air at High Humidity with the Formation of Unusual Quantum Dot Networks

Due to the practical applications of polymer solar cells (PSCs), their stability recently has received increasing attention. Herein, a new strategy was developed to largely enhance the long-term and thermal stability of PSCs in air with a relatively high humidity of 50-60% without any encapsulation. In this strategy, semiconductor PbS/CdS core/shell quantum dots (QDs) were incorporated into the photoactive blend of poly(3-hexylthiophene) (P3HT) and phenyl-C₆₁-butyric acid methyl ester (PCBM). By replacing the initial ligands of oleic acid with halide ligands on the surface of PbS/CdS QDs via solution-phase ligand exchange, we were able to form unusual, continuous QD networks in the film of P3HT:PCBM, which effectively stabilized the photoactive layer. Air-processed PSCs based on the stabilized P3HT:PCBM film showed excellent long-term stability under high humidity, providing over 3% of power conversion efficiency (PCE) simultaneously. Around 91% of pristine PCE was retained after 30 days storage in high-humidity air without encapsulation. This constitutes a remarkable improvement compared to ∼53% retained PCE for the QD-free devices, which can be ascribed to the efficient suppression of both PCBM aggregation and oxidation of the thiophene ring in P3HT, thanks to the formation of robust QD networks. Furthermore, the presence of QD networks was able to enhance the stability of the P3HT:PCBM film against thermal stress/oxidation under high-humidity environment (50-60%) as well. The device kept 60% of pristine PCE after thermal treatment for 12 h at 85 °C in air, which is more than twice higher than that for the QD-free device. To the best of our knowledge, the work represents the first unambiguous demonstration of the formation of QD networks in the photoactive layer and of their important contribution to the stability of PSCs. This strategy is highly promising for other fullerene-based PSCs and opens a new avenue toward achieving PSCs with high PCE and excellent stability.

Distribution and incorporation mode of the herbicide MCPA in soil derived organo-clay complexes

The incorporation of xenobiotics into soil, especially via covalent bonds or sequestration has a major influence on the environmental behavior including toxicity, mobility, and bioavailability. The incorporation mode of 4-chloro-2-methylphenoxyacetic acid (MCPA) into organo-clay complexes has been investigated under a low (8.5 mg MCPA/kg soil) and high (1000 mg MCPA/kg soil) applied concentration, during an incubation period of up to 120 days. Emphasis was laid on the elucidation of distinct covalent linkages between non-extractable MCPA residues and humic sub-fractions (humic acids, fulvic acids, and humin). The cleavage of compounds by a sequential chemical degradation procedure (OH^-, BBr₃, RuO₄, TMAH thermochemolysis) revealed for both concentration levels ester/amide bonds as the predominate incorporation modes followed by ether linkages. A possible influence of the soil microbial activity on the mode of incorporation could be observed in case of the high level samples. Structure elucidation identified MCPA as the only nonextractable substance, whereas the metabolite 4-chloro-2-methylphenol was additionally found as bioavailable and bioaccessible compound.

A hundred years in the elucidation of the structures of natural products

The development in the strategies for elucidating the structures of natural products from 1916 to 2016 are reviewed revealing the transition from chemical to spectroscopic methods and using examples drawn from the chemistry of terpenoids and steroids.

Mechanisms for 1,3-Dichloropropene Dissipation in Biochar-Amended Soils

Biochar, which is organic material heated under a limited supply of oxygen, has the potential to reduce fumigant emissions when incorporated in the soil, but the mechanisms are not fully understood. The objective of this study was to determine the effects of biochar properties, amendment rate, soil microbe, moisture, temperature, and soil type on the fate of 1,3-dichloropropene (1,3-D) isomers in laboratory incubation experiments by assessing the 1,3-D degradation rate and adsorption capacity. 1,3-D dissipation rates were significantly reduced due to strong adsorption by biochar, which was also strongly affected by biochar type. Following a 1% biochar amendment, the half-lives of 1,3-D in soil were increased 2.5-35 times. The half-lives of 1,3-D in soil were strongly affected by soil moisture, temperature, and amendment rate. The effects of sterilization on 1,3-D degradation were much smaller in biochar-amended soils than in nonsterilized soils, which suggests the importance of abiotic pathways with biochar's presence. Dissipation of 1,3-D in biochar was divided into adsorption (49-93%) and chemical degradation pathways. Biochar properties, such as specific surface area (SSA), pH, water content, carbon content, and feedstock, all appeared to affect 1,3-D dissipation with potentially complex interactions. The biochar (air-dry) water content was highly correlated with 1,3-D adsorption capacity and thus can serve as an important predictor for fumigant mitigation use. The fate of the adsorbed fumigant onto biochar requires further examination on potential long-term environmental impacts before guidelines for biochar as a field practice to control fumigant emissions can be formulated.

Photo, thermal and chemical degradation of riboflavin

Riboflavin (RF), also known as vitamin B₂, belongs to the class of water-soluble vitamins and is widely present in a variety of food products. It is sensitive to light and high temperature, and therefore, needs a consideration of these factors for its stability in food products and pharmaceutical preparations. A number of other factors have also been identified that affect the stability of RF. These factors include radiation source, its intensity and wavelength, pH, presence of oxygen, buffer concentration and ionic strength, solvent polarity and viscosity, and use of stabilizers and complexing agents. A detailed review of the literature in this field has been made and all those factors that affect the photo, thermal and chemical degradation of RF have been discussed. RF undergoes degradation through several mechanisms and an understanding of the mode of photo- and thermal degradation of RF may help in the stabilization of the vitamin. A general scheme for the photodegradation of RF is presented.

Durability tests of a fiber optic corrosion sensor

Steel corrosion is a major cause of degradation in reinforced concrete structures, and there is a need to develop cost-effective methods to detect the initiation of corrosion in such structures. This paper presents a low cost, easy to use fiber optic corrosion sensor for practical application. Thin iron film is deposited on the end surface of a cleaved optical fiber by sputtering. When light is sent into the fiber, most of it is reflected by the coating. If the surrounding environment is corrosive, the film is corroded and the intensity of the reflected signal drops significantly. In previous work, the sensing principle was verified by various experiments in laboratory and a packaging method was introduced. In this paper, the method of multiplexing several sensors by optical time domain reflectometer (OTDR) and optical splitter is introduced, together with the interpretation of OTDR results. The practical applicability of the proposed sensors is demonstrated in a three-year field trial with the sensors installed in an aggressive marine environment. The durability of the sensor against chemical degradation and physical degradation is also verified by accelerated life test and freeze-thaw cycling test, respectively.

Chemical stabilization of a Delta9-tetrahydrocannabinol prodrug in polymeric matrix systems produced by a hot-melt method: role of microenvironment pH

This research was conducted in order to fabricate stable polyethylene oxide (PEO)-based transmucosal systems of a Delta(9)-tetrahydrocannabinol (THC) prodrug, a hemisuccinate ester, using a hot-melt method. Since Delta(9)-tetrahydrocannabinol-hemisuccinate (THC-HS) was heat labile, a series of processing aids were evaluated in order to facilitate hot-melt production at lower temperatures, thereby reducing THC-HS degradation. The stability of THC-HS was influenced both by the processing conditions such as heating time and temperature, and the postprocessing storage conditions. The type of formulation additive also affected the extent of degradation. In the presence of polyethylene glycol (PEG)-400, the percentage of relative degradation of THC-HS to THC was 13.5% and 49.4% at 80 degrees C and 120 degrees C, respectively. In contrast, incorporation of vitamin E succinate (VES) reduced processing degradation to 2.1% and 9.2%, respectively, under the same conditions. Severe degradation of THC-HS was observed during storage, even under freezing conditions (-18 degrees C). A VES-Noveon AA-1 combination was observed to best stabilize the prodrug systems both during processing and postprocessing. Stabilization of THC-HS was achieved in these polyethylene oxide matrices at 4 degrees C, with almost 90% of theoretical drug remaining for up to 8 months. Investigation of the pH effect revealed that the pH of the microenvironment in these polymeric systems could be modulated to significantly improve the stability of THC-HS, degradation being the least in a relatively acidic medium.