Mild Degradation Research Articles

Simulated degradation of biochar and its potential environmental implications

A simulated oxidation technique was used to examine the impacts of degradation on the surface properties of biochar and the potential implications of the changes in biochar properties were discussed. To simulate the short- and long-term environmental degradation, mild and harsh degradation were employed. Results showed that after mild degradation, the biochar samples showed significant reductions in surface area and pore volumes. After harsh degradation, the biochar samples revealed dramatic variations in their surface chemistry, surface area, pore volumes, morphology and adsorption properties. The results clearly indicate that changes of biochar surface properties were affected by biochar types and oxidative conditions. It is suggested that biochar surface properties are likely to be gradually altered during environmental exposure. This implies that these changes have potential effects for altering the physicochemical properties of biochar amended soils.

Optimization of mobile phase for the determination of Esomeprazole and related compounds and investigation of stress degradation by LC–MS

In this study, the objective was to investigate the degradation behavior of Esomeprazole under different recommended stress conditions according to International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use [1] by HPLC. Our research showed that the effect of mobile phase species on separation was significant for the determination of Esomeprazole and its related compounds. Successful separation of the drug from its related impurities and degradation products formed under different stress conditions was achieved using ammonium acetate buffer/ACN by a gradient elution. Compared with phosphate buffer/ACN, ammonium acetate buffer/ACN under same pH and gradient showed a great improvement in resolution due to the change of elution order. The drug was subjected to stress conditions including acidic, alkaline, oxidative, photolytic, and thermal conditions. Extensive degradation occurred in acidic and oxidative conditions, while mild degradation was observed in alkaline and photolytic conditions. Besides, it turned out the drug was extremely stable under thermal condition. The stability-indicating LC-UV method was validated with respect to linearity, precision, accuracy, specificity, and robustness. The LC-MS method was also adopted for the characterization of degradation products. Based on the m/z values and fragmentation patterns, the degradation pathway of the drug has been proposed.

Bioactive Ca–P coating with self-sealing structure on pure magnesium

Bioactive coatings containing Ca and P with self-sealing structures were fabricated on the surface of pure magnesium using micro-arc oxidation technique (MAO) in a specific calcium hydroxide based electrolyte system. Coatings were prepared at three applied voltages, i.e. 360, 410 and 450 V, and the morphology, chemical composition, corrosion resistance and the degradation properties in Hank's solution of the MAO-coated samples with three different applied voltages were investigated. It was found that all the three coatings showed similar surface morphologies that the majority of micro-pores were filled with compound particles. Both the porous structures and the compound particles were found to contain consistent chemical compositions which were mainly composed of O, Mg, F, Ca and P. Electrochemical tests showed a significant increase in corrosion resistance for the three coatings, meanwhile the coating obtained at 450 V exhibited the superior corrosion resistance owing to the largest coating thickness. The long term immersion tests in Hank's solution also revealed an effective reduction in corrosion rate for the MAO coated samples, and the pH values of the coated samples always maintained a lower level. Besides, all the three coatings were subjected to a mild and uniform degradation, while the coating obtained at 360 V showed a relatively obvious degradation characteristic and appreciable Ca and P contents on the surfaces of the three coatings were observed after immersion in Hank's solution. The results of the present study confirmed that the MAO coatings containing bioactive Ca and P elements with self-sealing structures could significantly enhance the corrosion resistance of magnesium substrate in Hanks' solution with great potential for medical application.

Accounting for an Isobaric Interference Allows Correct Determination of Folate Vitamers in Serum by Isotope Dilution-Liquid Chromatography-Tandem MS

Mild and prolonged oxidative degradation of 5-methyltetrahydrofolate (5-methylTHF) leads to the biologically inactive pyrazino-s-triazine derivative of 4α-hydroxy-5-methylTHF (MeFox). MeFox and the biologically active 5-formyltetrahydrofolate (5-formylTHF) are isobaric compounds that behave similarly during chromatographic and mass separation, making coelution and misidentification likely. Our published routine liquid chromatography-tandem MS (LC-MS/MS) method did not discern between 5-formylTHF and MeFox, measuring the sum of these compounds at a mass to charge ratio (m/z) of 474→327 as 5-formylTHF. We modified this method to separate MeFox and 5-formylTHF by either chromatography or unique mass transitions and then applied the 2 methods to serum specimens to determine typical concentrations of these compounds. The 2 unique transitions (m/z: 5-formylTHF, 474→299; MeFox, 474→284) showed good sensitivity [limit of detection (nmol/L): 5-formylTHF, 0.21; MeFox, 0.34], selectivity (no interfering peaks), spiking recovery (mean ± SD: 5-formylTHF, 103 ± 3.4%; MeFox, 94 ± 10%), and low imprecision (CV: 5-formylTHF, 3.9% at 2.4 nmol/L; MeFox, 5.1% at 2.9 nmol/L). The mass separation method detected 5-formylTHF in the same specimens as the chromatographic separation method. Analysis of several thousand serum specimens showed that the majority (∼85%) contained MeFox at <3 nmol/L but no detectable 5-formylTHF concentrations, some (∼14%) contained 5-formylTHF at <0.5 nmol/L, and a few specimens contained 5-formylTHF at >1 nmol/L and MeFox at >10 nmol/L. In summary, serum can contain 5-formylTHF high enough to contribute to total folate and contains MeFox that will bias total folate if not appropriately separated. Including measurements of MeFox and 5-formylTHF along with the other folate vitamers will enhance assessments of the association between biologically active folate and health effects.

Responsive release of polyanions from soluble aggregates formed with a hydrolyzable cationic surfactant and a nonionic surfactant

Soluble aggregates formed in dilute aqueous mixtures of polyacrylate (PA), the cationic surfactant decyl betainate (DB), and the nonionic surfactant octaethylene glycol monododecyl ether (C12E8) have been characterized. The aggregates formed can be viewed as mixed micelles of DB and C12E8 with the cationic charge of DB being largely neutralized by PA condensed on the micellar surface. DB contains an ester bond that is susceptible to base-catalyzed hydrolysis under mild alkaline conditions and degradation of DB leads to a decreased attraction of PA to the mixed micelles. It is shown that (1) an increasing extent of DB hydrolysis gives a gradual increase in the fraction of PA released from the mixed aggregates to the surrounding solution, and (2) the rate of hydrolysis, and thus the rate of polymer release, can be controlled by pH. The presented principle can potentially be used in controlled release devices.

Changes in the physical properties of xanthan gum induced by a dynamic high-pressure treatment

The effect of microfluidization, a dynamic high pressure treatment, on xanthan gum was investigated in views of enlarging its potential applications. Samples were characterized chemically and physically (molecular weight, intrinsic viscosity, flow behavior and flow induced birefringence). Particular interest was given to the correlation between the level of degradation and aggregate content to the flow behavior and flow-induced birefringence. A mechanism of degradation is proposed: initially, microfluidization reduces the aggregated state of xanthan and may even be able to dissociate the double helical structure into single chains; upon increasing treatment severity, a relatively mild degradation of the main chain can be achieved. Interestingly, samples treated at high ionic strengths were more sensitive to mechanical degradation, arguably since stiffer molecules in the ordered conformation presented a larger exposed surface and thus experienced stronger effective stresses when subjected to the high shear and cavitation forces present in the microfluidization chamber.

Multistep degradation method for β-O-4 linkage in lignins: γ-TTSA method. Part 2: reaction of lignin model polymer (DHP)

Abstract A selective cleavage method for β-O-4 linkages (the γ-TTSA method) was introduced in previous works, which consists of four reaction steps: (1) γ-tosylation, (2) thioetherification, (3) sulfonylation, and (4) mild alkali degradation. This method was applied to the degradation of a lignin polymer model (dehydrogenation polymer, DHP) consisting of guaiacyl units. Each reaction step was followed by Fourier transform infrared (FT-IR) spectroscopy and heteronuclear single quantum coherence nuclear magnetic resonance (HSQC-NMR) spectroscopy. It was demonstrated that only the β-O-4 linkage was selectively cleaved by the γ-TTSA method, although other linkages, such as β-5 and β-β linkages, were also present in the DHP. Consequently, the γ-TTSA method is expected to be also useful for the degradation of native lignins.

The N400 and Late Positive Complex (LPC) Effects Reflect Controlled Rather than Automatic Mechanisms of Sentence Processing

This study compared automatic and controlled cognitive processes that underlie event-related potentials (ERPs) effects during speech perception. Sentences were presented to French native speakers, and the final word could be congruent or incongruent, and presented at one of four levels of degradation (using a modulation with pink noise): no degradation, mild degradation (2 levels), or strong degradation. We assumed that degradation impairs controlled more than automatic processes. The N400 and Late Positive Complex (LPC) effects were defined as the differences between the corresponding wave amplitudes to incongruent words minus congruent words. Under mild degradation, where controlled sentence-level processing could still occur (as indicated by behavioral data), both N400 and LPC effects were delayed and the latter effect was reduced. Under strong degradation, where sentence processing was rather automatic (as indicated by behavioral data), no ERP effect remained. These results suggest that ERP effects elicited in complex contexts, such as sentences, reflect controlled rather than automatic mechanisms of speech processing. These results differ from the results of experiments that used word-pair or word-list paradigms.

Thermal stability of polycarbonate-graphene nanocomposite foams

A thermogravimetric study in both nitrogen and air atmospheres has been carried out on unfilled and graphene-reinforced solid and foamed polycarbonate. Polycarbonate foams were prepared using a supercritical CO2 dissolution one-step batch foaming process. Results showed that polycarbonate displayed a characteristic one-step decomposition under nitrogen, while three-step degradation was observed in air. In addition, as-received pristine graphene nanoplatelets displayed a three-step degradation in air, compared to a mild degradation under nitrogen. It was found that the thermal stability remarkably improved for the foamed composites, related to a combination of a heat transfer reduction promoted by the insulating cellular structure and the presence of the platelet-like graphene, which helped create a physical barrier effect, delaying the escape of volatile products generated during decomposition.

Split-belt walking: adaptation differences between young and older adults

Human walking is highly adaptable, which allows us to walk under different circumstances. With aging, the probability of falling increases, which may partially be due to a decreased ability of older adults to adapt the gait pattern to the needs of the environment. The literature on visuomotor adaptations during reaching suggests, however, that older adults have little problems in adapting their motor behavior. Nevertheless, it may be that adaptation during a more complex task like gait is compromised by aging. In this study, we investigated the ability of young (n = 8) and older (n = 12) adults to adapt their gait pattern to novel constraints with a split-belt paradigm. Findings revealed that older adults adapted less and more slowly to split-belt walking and showed fewer aftereffects than young adults. While young adults showed a fast adjustment of the relative time spent in swing for each leg older adults failed to do so, but instead they were very fast in manipulating swing speed differences between the two legs. We suggest that these changes in adaptability of gait due to aging stem from a mild degradation of cortico-cerebellar pathways (reduced adaptability) and cerebral structures (decreased ability to change gait cycle timing). However, an alternative interpretation may be that the observed reduced adaptation is a compensatory strategy in view of the instability induced by the split-belt paradigm.

Multiple-sourced features of marine oils in the Tarim Basin, NW China – Geochemical evidence from occluded hydrocarbons inside asphaltenes

The Tarim Basin, NW China, is a large composite basin with multiple sets of petroleum source rocks. The basin has undergone numerous episodes of hydrocarbon generation, migration and accumulation, making it difficult to assess the source rocks and oil–source correlation for the widespread marine oils in this area.Protected by the molecular structure of asphaltenes, occluded hydrocarbons can provide information about the early source rocks. In this work, the occluded hydrocarbons released from the asphaltenes by a mild chemical degradation method were compared with the crude oil maltenes and the adsorbed compounds from asphaltenes. Analysis of biomarker distribution and the carbon isotope composition of individual n-alkanes suggests that the widespread marine oils in the Tazhong Uplift, Tabei Lunnan Uplift and Halahatang Depression were contributed by Cambrian–Lower Ordovician source rocks at an early stage, and later mixed with hydrocarbons derived from Middle-Upper Ordovician source rocks. The marine oils in the Tarim Basin demonstrate extensive characteristics of having been derived from multiple source rocks.

Multi-steps degradation method for β-O-4 linkage in lignins: γ-TTSA method. Part 1: Reaction of non-phenolic dimeric β-O-4 model compounds

Abstract The so-called γ-TTSA method has been developed for the cleavage of β-O-4 linkages in lignin. It consists of four steps: (1) γ-tosylation, (2) thioetherification (substitution reaction with 1-dodecanethiol to γ-thioether), (3) sulfonylation (oxidation from γ-thioether to γ-sulfone), and (4) mild alkali degradation of γ-sulfone. The method was tested on non-phenolic dimeric β-O-4 lignin model compounds: 1G (4-benzyloxy-3-methoxyphenylglycerol-β-guaiacyl ether), 1S (4-benzyloxy-3,5-dimethoxyphenylglycerol-β-syringyl ether), and 1H (4-benzyloxyphenylglycerol-β-phenyl ether). It is demonstrated that the mild alkali degradation of the γ-sulfone group proceeds efficiently, i.e., the electron-withdrawing sulfone group at γ-position contributes to the cleavage of β-O-4 linkages. The γ-TTSA method may be especially useful for the elucidation of lignin-carbohydrate complex structures containing benzylether bonds.

Evaluation of Stability of 5- Fluorouracil under Different Stress Conditions: High Performance Liquid Chromatography and Infrared Spectroscopic Approach

5-fluorouracil is one of the most widely used chemotherapeutic agents for the treatment of several types of cancer. The present study describes the determination of stability of 5-fluorouracil under different stress conditions using high performance liquid chromatography (HPLC) and infrared (IR) spectroscopy. The separation of 5-fluorouracil was carried out on a C18 reverse phase column using 40 mM KH2PO4 as mobile phase. The ultraviolet detection wavelength was 260 nm. The HPLC method was validated and the response of the drug was linear in the concentration range of 20 μg ml-1 to 550 μg ml-1 with a correlation coefficient of 0.9995. The % R.S.D. values for intra-day and inter-day precision were determined as < 0.2% and < 1% respectively. Infrared spectroscopic measurements were carried out in diffuse reflectance and attenuated total reflectance (ATR) modes. The study reveals that 5-flurouracil shows mild degradation up to 275°C and major degradation at about 285°C. It undergoes a degradation of about 22% when exposed to stress conditions of acidic hydrolysis. A major degradation of about 97% was observed under alkaline condition. The drug undergoes degradation from 26% to 41% when exposed to oxidative condition. The drug remains stable when exposed to UV irradiations.

Development and validation of stability indicating UPLC assay method for ziprasidone active pharma ingredient

Background: Ziprasidone, a novel antipsychotic, exhibits a potent highly selective antagonistic activity on D2 and 5HT2A receptors. Literature survey for ziprasidone revealed several analytical methods based on different techniques but no UPLC method has been reported so far. Aim: Aim of this research paper is to present a simple and rapid stability indicating isocratic, ultra performance liquid chromatographic (UPLC) method which was developed and validated for the determination of ziprasidone active pharmaceutical ingredient. Forced degradation studies of ziprasidone were studied under acid, base, oxidative hydrolysis, thermal stress and photo stress conditions. Materials and Methods: The quantitative determination of ziprasidone drug was performed on a Supelco analytical column (100×2.1 mm i.d., 2.7 ΅m) with 10 mM ammonium acetate buffer (pH: 6.7) and acetonitrile (ACN) as mobile phase with the ratio (55:45-Buffer:ACN) at a flow rate of 0.35 ml/ min. For UPLC method, UV detection was made at 318 nm and the run time was 3 min. Developed UPLC method was validated as per ICH guidelines. Results and Conclusion: Mild degradation of the drug substance was observed during oxidative hydrolysis and considerable degradation observed during basic hydrolysis. During method validation, parameters such as precision, linearity, ruggedness, stability, robustness, and specificity were evaluated, which remained within acceptable limits. Developed UPLC method was successfully applied for evaluating assay of Ziprasidone active Pharma ingredient.

Multivariate analysis of cartilage degradation using the support vector machine algorithm

An important limitation in MRI studies of early osteoarthritis is that measured MRI parameters exhibit substantial overlap between different degrees of cartilage degradation. We investigated whether multivariate support vector machine analysis would permit improved tissue characterization. Bovine nasal cartilage samples were subjected to pathomimetic degradation and their T(1), T(2), magnetization transfer rate (k(m) ), and apparent diffusion coefficient (ADC) were measured. Support vector machine analysis performed using certain parameter combinations exhibited particularly favorable classification properties. The areas under the receiver operating characteristic (ROC) curve for detection of extensive and mild degradation were 1.00 and 0.94, respectively, using the set (T(1), k(m), ADC), compared with 0.97 and 0.60 using T(1), the best univariate classifier. Furthermore, a degradation probability for each sample, derived from the support vector machine formalism using the parameter set (T(1), k(m), ADC), demonstrated much stronger correlations (r(2) = 0.79-0.88) with direct measurements of tissue biochemical components than did even the best-performing individual MRI parameter, T(1) (r(2) = 0.53-0.64). These results, combined with our previous investigation of Gaussian cluster-based tissue discrimination, indicate that the combinations (T(1), k(m)) and (T(1), k(m), ADC) may emerge as particularly useful for characterization of early cartilage degradation.

Effectiveness of ecological restoration projects in Horqin Sandy Land, China based on SPOT-VGT NDVI data

Horqin Sandy Land is a major source of sandstorms in Northern China, especially the Beijing–Tianjin–Tangshan Region. A series of ecological restoration projects including the ‘Grain for Green Project’, the ‘Beijing and Tianjin Sandstorm Source Controlling Project’, and the ‘Three-North Shelterbelt Project’ were implemented in this region. This study assesses the effectiveness of ecological restoration projects within Tongliao City, the main body of Horqin Sandy Land. The different treatment effects of various sand dunes were assessed and compared based on Normalized Difference Vegetation Index (NDVI) from SPOT VEGETATION Ten Daily Synthesis Archive from 1999 to 2007 and the desert distribution map of China in 2000. The results showed that: (1) the fixed and semi-fixed sand dunes were the main sand dune types, which accounted for 70% of the entire sand dune area in 2000; followed by shifting sand dunes and the semi-shifting sand dunes. (2) The ecological restoration projects resulted in improvements of different sand dune types, the improved area covered 76% of the sand dune area, mainly in the southern parts of the study area. The vegetation cover of the sand dunes in Naiman Banner, Hure Banner and the south of Horqin Left Back Banner increased significantly. While mild improvement occurred in the central sand dunes of the study area. (3) The area with degraded vegetation accounted for approximately 10% of sand dune area, mainly located in the southeast of Jarud Banner and the west of Horqin Left Middle Banner. Most of these areas showed mild and insignificant degradation except for a small area of moderate degradation. (4) The types of sand dunes in degraded status were mainly the fixed and semi-fixed sand dunes, followed by the semi-shifting sand dunes and saline-alkali land. The lower the dune fixity (e.g. shifting or semi-shifting versus semi-fixed or fixed) and the more likely to contribute to sand-storms, the greater the effectiveness of restoration projects. Finally, some implications for the sustainable development of the ecological restoration projects are discussed.

HPLC AND LC-MS STUDIES ON STRESS DEGRADATION BEHAVIOR OF LEVOCETIRIZINE AND DEVELOPMENT OF A VALIDATED SPECIFIC STABILITY-INDICATING METHOD

The objective of the current investigation was to study the degradation behavior of levocetirizine under different ICH recommended stress conditions using HPLC and LC-MS and to establish a validated stability-indicating method. The drug was subjected to stress conditions of hydrolysis, photolysis, and thermal decomposition. Extensive degradation was found to occur in photolytic stress conditions. Mild degradation was observed in acidic, alkaline, and neutral conditions. The drug was stable to thermal stress condition. Successful separation of drugs from degradation products formed under stress conditions was achieved on a C-18 Supelco® Column using water-acetonitrile (50:50%v/v) as the mobile phase. The flow rate was 1.0 mL/min and the detection wavelength was 230 nm. The degradant products were characterized by LC-MS. The method was validated with respect to linearity, precision, accuracy, specificity, and robustness. The developed method efficiently separated the drug and degradation product in actual samples.

Enhanced Lithium-Ion Intercalation Properties of V2O5 Xerogel Electrodes with Surface Defects

V2O5 xerogel films were fabricated by casting V2O5 sols onto fluorine-doped tin oxide (FTO) glass substrates and annealing at 300 °C for 3 h in different annealing atmospheres of air and nitrogen. Films prepared in different annealing conditions possess different grain sizes and crystallinity, while the vanadium ion oxidation state also varies, as identified by X-ray absorption spectroscopy. A nitrogen annealing atmosphere induces the presence of defects, such as V4+ ions, and associated oxygen vacancies. Thus, the presence of defects, whether on the film surface or in the bulk, can be controlled by using air and nitrogen annealing atmospheres in the proper order. Electrochemical impedance analyses reveal enhanced charge-transfer conductivity in films with more V4+ and oxygen vacancies on the film surface, that is, a film annealed, first, for 0.5 h in air and then for 2.5 h in nitrogen. Lithium-ion intercalation measurements show that, at a charge/discharge current density of 600 mA g−1, this film possesses a noticeably better lithium-ion storage capability than films without surface defects. This sample starts with an initial discharge capacity of 139 mA h g−1, and the capacity increases slowly to a maximum value of 156 mA h g−1 in the 15th cycle, followed by a mild capacity degradation in later cycles. After 50 cycles, the discharge capacity is still as high as 136 mA h g−1. A much improved lithium-ion intercalation capacity and cyclic stability are attributed to V4+ surface defects and associated oxygen vacancies introduced by N2 annealing.

Optimized water treatment by combining catalytic Fenton reaction using diamond supported gold and biological degradation

Recently it has been reported that gold nanoparticles supported on Fenton treated diamond nanoparticles (Au/DNP) is a highly efficient catalyst to promote the generation of hydroxyl radicals from H2O2 [S. Navalon, R. Martin, M. Alvaro, H. Garcia, Angew. Chem. Int. Ed. 49 (2010) 8403–8407]. In the present work we have optimized a series of experimental parameters including initial pH, reaction temperature, H2O2 concentration, phenol to gold mol ratio and oxygen pressure to achieve biodegradability of aqueous phenol solutions with the minimum H2O2 concentration and attain a complete lack of toxicity (determined by the Vibrio fischeri bioluminescence assay). The results presented show how to combine mild Fenton degradation of bioreluctant phenol with consecutive biological treatment in such a way that the amount of H2O2 is kept to the minimum value. It was determined that the best conditions are pH 4, 50°C, H2O2 to phenol molar ratio 4 and 320mgL−1 (1wt% Au) catalyst under oxygen atmosphere. Au/DNP exhibits a remarkable stability under these conditions and can be used up to four times without observing any loose of catalytic activity as determined by the temporal profiles of phenol degradation and H2O2 decomposition.

Development and Validation of Stability Indicating RP-HPLC-PDA Method for Tenatoprazole and Its Application for Formulation Analysis and Dissolution Study

In the present study, comprehensive stress testing of tenatoprazole was carried out according to ICH guide-line Q1A (R2). Tenatoprazole was subjected to stress conditions of hydrolysis, oxidation, photolysis and neutral decomposition. Extensive degradation was found to occur in acidic, neutral and oxidative conditions. Mild degradation was observed in basic conditions. The drug is relatively stable in the solid-state. Successful separation of drug from degradation products formed under stress conditions was achieved on a Kromasil C18 column (250 mm × 4.6 mm, 5.0 μ particle size) using methanol: THF: acetate buffer (68:12:20 v/v) pH adjusted to 6.0 with acetic acid as mobile phase, flow rate was 1.0 mL●min–1 and column was maintained at 45°C. Quantification and linearity was achieved at 307 nm over the concentration range of 0.5 - 160 μg●mL–1 for tenatoprazole. The method was validated for specificity, linearity, accuracy, precision, LOD, LOQ and robustness.