Kinetic Study Of Degradation Research Articles

Comparative study of catalytic performance and degradation kinetics of biodiesels produced using heterogeneous catalysts from kaolinite

This study comparatively investigates the catalytic activities and degradation kinetics of the produced biodiesels using kaolinite-based heterogeneous catalysts to examine the stability. The performance of the catalysts was tested under the same operating parameter (methanol/oil ratio, 5:1, at 200 °C for 6 h). The obtained biodiesel was analyzed using TGA equipment to obtain the yield, as well as the degradation kinetic parameters. It was observed that the solid superacid SHY zeolite gave the highest biodiesel yield (90.76%) because of higher acid strength. The catalysts performance is in the order of HY<ALK<HLK<NaLK<SHY zeolite. The lower performance of HY (72.42% yield) is attributed to the presence of high basic sites, being that shea butter has high FFA. The degradation kinetics of each biodiesel sample was performed using the TGA data to examine the thermal and oxidative stability. The frequency factor (A), activation energy, and reaction order were determined by employing the Coats-Redfern model. It was observed that first-order reaction mechanism can satisfactorily describe all the biodiesel kinetics. Further, the biodiesel from SHY zeolite gives the highest EA (98.65 kJ/mol). This result indicates that SHY zeolite is the best catalyst in terms of biodiesel yield and stability.

Understanding of cabotegravir degradation through isolation and characterization of key degradation products and kinetic studies

Cabotegravir is a novel human immunodeficiency virus integrase enzyme inhibitor used for prevention and treatment of HIV infection. The combinational final dosage form, as extended release injection suspension in combination with rilpivirine and as cabotegravir tablets (for lead-in therapy), was recently approved in Canada, EU and in USA and is currently seeking approval also in other countries. The subject of this investigation was to study the degradation of cabotegravir under different stress conditions as per the International Council for Harmonization (ICH) guidelines. The drug substance was found to be stable in thermal, photolytic and basic stress conditions, but degraded under acidic and oxidative stress conditions. It was determined that four main degradation products of cabotegravir are formed in forced degradation studies. All four main degradation products were isolated using preparative chromatography and subjected to NMR and HRMS analysis in order to determine their structure. We proposed degradation pathways of cabotegravir under acidic stress conditions in solution based on the structure of isolated degradation products, cabotegravir degradation kinetic studies and degradation studies on two isolated key degradation products. Moreover, degradation pathway to predominant oxidation degradation product is proposed based on the adduct of cabotegravir and peroxide species, which was identified by LC-HRMS analysis. This is the first report to the best of our knowledge that describes characterized cabotegravir forced degradation impurities and provides insights into its degradation pathways.

A mechanistic explanation on degradation behavior of flibanserin for identification and characterization of its potential degradants using LC-DAD/ESI/APCI-Q-TOF-MS/MS

Sprout Pharmaceuticals got marketing approval for Flibanserin (FLB) from USFDA. It is a well-known fact that post-marketing research on impurity profiling significantly contributes to the improvement of quality, safety and efficacy of a drug. In this study, we performed a comprehensive forced degradation of FLB to identify and characterize its degradation impurities and establish the degradation pathways. All the potential degradation impurities were chromatographically separated and identified. Five new potential degradation products (DPs) were characterized using LC-DAD/ESI/APCI-Q-TOF-MS/MS. The plausible structure for all the DPs has been established employing their mass fragmentation pattern. Elemental compositions of the DPs were derived from accurate mass measurements and mass error in ppm. A probable mechanistic explanation has been established for formation of the DPs. Till date, no study has been reported on the degradation behavior of FLB before this. The degradation profiling of FLB reported in this study will provide a complete understanding of the entire possible degradation impurities of FLB. One or more identified degradation impurities can be recommended by the regulatory bodies as the marker for stability study of FLB. The analytical method we have developed can be used for routine quality control of this molecule to quantitate it in presence of their potential impurities. In continuation to this research, degradation kinetic study of FLB to establish the degradation behavior in different stress conditions, mass balance study to correlate the amount loss of parent drug with formation of DPs and evaluation of toxicity potential of the DPs are recommended to be conducted in future.

Synthesis, Spectral and Thermal Degradation Kinetics Studies of Copolymer Resin

Synthesis, Spectral and Thermal Degradation Kinetics Studies of Copolymer Resin

Evaluation of physicochemical stability and degradation kinetics of bedaquiline in hydrolytic solutions of different pH

BackgroundTuberculosis is an infection that has high mortality rate in human as well as in animals if it remains unattained for long time. Scientists are always desirous to discover new molecules against Mycobacterium tuberculosis; one of them is bedaquiline which was recently approved to treat multidrug resistance TB. During the clinical study of new molecule stability and impurity are the key aspects to develop formulation. Stability issues in bulk drug are dangerous to drug safety and needs careful attention in formulation development. Bedaquiline stability study was completed with reversed-phase high-performance liquid chromatography (HPLC) and utilized in degradation kinetic study of bedaquiline in aqueous condition under different pH, temperature, and concentrations of degradant.ResultsLinearity was obtained in 50.0-250.0μg/ml, correlation coefficient, and regression line equation were 0.998 and Y=18528x + 7E+06 respectively. Intraday, inter day precision, and repeatability RSD were less than 2.0%. Average recovery in accuracy study was more than 98.0% showed that good recovery was obtained. Degradation kinetics parameters like activation energy (Ea), half-life (t50), rate constant (k), and shelf life (t90) were calculated under different condition for bedaquiline. Entropy and enthalpy of reaction was studied to gather knowledge about energy of system.ConclusionThe result explained that bedaquiline degradation was pH-dependant, as increase in concentration of degradant and temperature, there was increase in degradation rate of bedaquiline. Bedaquiline was stable in neutral aqueous condition and at lower temperatures, shows that drug is hydrophobic in nature. Kinetic data showed that bedaquiline followed first order kinetics in acidic and alkaline pH.

Titania containing natural clay doped with carbon nanotubes for enhanced natural photocatalytic discoloration of wastewater

Water contamination with dyes is harmful to humans and the environment. This study investigated the photocatalytic activity of natural clay (GOL) mixed with carbon nanotubes (CNT) for removal of brilliant black (BB) in wastewater. The materials were characterized with FESEM-EDS, XRD, XRF, FTIR and UV-vis DRS. The natural clay contains 2.34 % TiO2 which is 75% more than most natural clays. SEM showed that CNT were well dispersed and mixed with clay. DRS spectra showed two absorption bands above 380 nm. CNT in GOL has decreased significantly the energy band gaps from 2.75 and 3.25 eV to 1.53 and 2.90 eV for GOL and 10% CNT–GOL, respectively. Photocatalytic activity was enhanced with degradation of BB increased from 66 to 95% with GOL and 10% CNT–GOL respectively after 45 min of visible light irradiation. The improvement can be attributed to the synergy of the interface heterojunction of clay and CNT. The presence of CNT reduces the e− and h+ (e− / h+) pairs recombination and facilitates the production of reactive oxygen species responsible for the decay of dye. The addition of H2O2 to the experiment (2 mmoL) confirmed the role of holes and hydroxyl radicals. Eighty-five percent of BB carbon content was removed with 10% CNT–GOL suggesting that mineralization occurred. After 45 min of visible light irradiation, the degradation kinetic studies followed a second-order reaction with a R2 = 0.997. Therefore, natural clay–CNT nanocomposites can be applied to treat dyes containing wastewaters.

Degradation kinetic study of ZIF-8 microcrystals with and without the presence of lactic acid.

The zeolitic imidazolate framework ZIF-8 (Zn(mim)2, mim = 2-methylimidazolate) has recently been proposed as a drug delivery platform for anticancer therapy based on its capability of decomposing in acidic media. The concept presumes a targeted release of encapsulated drug molecules in the vicinity of tumor tissues that typically produce secretions with elevated acidity. Due to challenges of in vivo and in vitro examination, many studies have addressed the kinetics of ZIF-8 decomposition and subsequent drug release in phosphate buffered saline (PBS) with adjusted acidity. However, the presence of hydrogen phosphate anions [HPO4]2− in PBS may also affect the stability of ZIF-8. As yet, no separate analysis has been performed comparing the dissolving capabilities of PBS and various acidification agents used for regulating pH. Here, we provide a systematic study addressing the effects of phosphate anions with and without lactic acid on the degradation rate of ZIF-8 microcrystals. Lactic acid has been chosen as an experimental acidification agent, since it is particularly secreted by tumor cells. Interestingly, the effect of a lactic acid solution with pH 5.0 on ZIF-8 degradation is shown to be weaker compared to a PBS solution with pH 7.4. However, as an additive, lactic acid is able to enhance the decomposition efficacy of other solutions by 10 to 40 percent at the initial stage, depending on the presence of other ions. Additionally, we report mild toxicity of ZIF-8 and its decomposition products, as examined on HDF and A549 cell lines.

Thermal stability, degradation kinetic and electrical properties studies of decorated graphene oxide with CeO2 nanoparticles-reinforced epoxy coatings

We synthesized decorated graphene oxide with CeO2 nanoparticles (CeO2-GO) hybridusing silane coupling agents, then we dispersed them in the epoxy resin after optimizing it at a weight fraction %1 using differential scanning calorimetry (DSC). The structural and morphological characterization was evaluated using Fourier Transform Infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and X-ray diffraction. The thermal stability of CeO2-GO/Epoxy (CGE) and neat epoxy (NE) were studied by TGA analyses and showed that the CGE system has a good thermal stability and higher char yield comparing to the NE system. The degradation kinetic parameters for CGE matrix were computed by the Vyazovkin’s advanced isoconversional method. The master plots as model fitting was used to estimate the thermal decomposition mechanism, and the results show a good agreement between the experimental data and the F1 theoretical model. We have used electrical impedance spectroscopy (EIS) to evaluate electrical resistance of the CGE system at different percent of (CeO2-GO) nanoparticle. This research highlights that the (CeO2-GO) nanoparticleis a promising candidate for fabrication of anticorrosive coatings.

Method development, degradation pathway and kinetic of capecitabine

The present work describes a simple, accurate and precise Stability indicating RP-HPLC method for the estimation of Capecitabine (CPT) in bulk and pharmaceutical formulation. The Mobile phase used was Acetonitrile: Water (60: 40v/v) with 1ml/min. flow rate and 240nm was used as a wavelength maximum. The C18 HS (250 X 4.6) mm, 5 µm column was used as a stationary phase. The method was validated as per the ICHQ2 Guidelines. The retention time of CPT was found to be 3.3 min. A linear response was observed in the range of 10-50 ?g/mL with a regression coefficient of 0.999. The LOD and LOQ were found to be 1.43?g/mL and 4.34?g/mL respectively. This method can be used for the determination of CPT in quality control of API and dosage form without interference of the excipients, impurities and degradation products and hence can be used as stability indicating assay method. CPT was subjected to degradation under different stress conditions recommended by ICH viz acid, alkali, photolytic, dry heat and oxidative condition. The samples so generated were used for degradation studies including degradation kinetic study using the developed method. The degradation pathway of CPT was found to be acid hydrolysis and temperature exceeding 100°c. The degradation kinetic study shows that the acid hydrolysis, alkaline hydrolysis and oxidative degradation of the CPT follow first order kinetic. Keywords: Anticancer drug, Capecitabine, Degradation, Stability indicating assay method, Validation.

Isolation and Molecular Characterization of Polycyclic Aromatic Hydrocarbon Degrading Bacteria from Effluent Water from Weras River Park, Sri Lanka

The present study records the detection of PAHs such as naphthalene and anthracene and isolation of PAHs degrading bacteria from a restaurant site, Weras River Park, in Boralesgamuwa, Sri Lanka. Water samples were collected in seven locations of the study area. Water temperature (oC), pH, and electric conductivity (EC) were measured at the site itself using standard meters. Nitrogen nitrate (N-NO3-) and total phosphate (TP) were measured at the laboratory following the standard methods. Following the extraction of PAHs in collected water samples, detection was carried out using the PDA-HPLC diode array method. PAH degrading bacteria were identified using microplate assay. The selected bacteria strains were subjected to degradation kinetic studies following molecular identification by 16S rRNA analysis. Phylogenetic analysis identified Achromobacter spanius as potential naphthalene degrading bacteria, where Alcaligens faecalis was recorded as an anthracene degrader. Degradation study confirmed that A. spanius efficiently degraded naphthalene at the rate of 0.145±0.002 ppm/day, whereas A. faecalis degraded anthracene at the rate of 0.181±0.036 ppm/day, respectively. Degradation of structures of the Naphthalene and Anthracene by A. spanius and A. faecalis was further analyzed by Fourier Transform Infrared Spectroscopy (FTIR). This is the first record on naphthalene degradation by the bacterium A. spanius.

CDK Family PROTAC Profiling Reveals Distinct Kinetic Responses and Cell Cycle-Dependent Degradation of CDK2.

Targeted protein degradation using heterobifunctional proteolysis-targeting chimera (PROTAC) compounds, which recruit E3 ligase machinery to a target protein, is increasingly becoming an attractive pharmacologic strategy. PROTAC compounds are often developed from existing inhibitors, and assessing selectivity is critical for understanding on-target and off-target degradation. We present here an in-depth kinetic degradation study of the pan-kinase PROTAC, TL12-186, applied to 16 members of the cyclin-dependent kinase (CDK) family. Each CDK family member was endogenously tagged with the 11-amino-acid HiBiT peptide, allowing for live cell luminescent monitoring of degradation. Using this approach, we found striking differences and patterns in kinetic degradation rates, potencies, and Dmax values across the CDK family members. Analysis of the responses revealed that most of the CDKs showed rapid and near complete degradation, yet all cell cycle-associated CDKs (1, 2, 4, and 6) showed multimodal and partial degradation. Further mechanistic investigation of the key cell cycle protein CDK2 was performed and revealed CDK2 PROTAC-dependent degradation in unsynchronized or G1-arrested cells but minimal loss in S or G2/M arrest. The ability of CDK2 to form the PROTAC-mediated ternary complex with CRBN in only G1-arrested cells matched these trends, despite binding of CDK2 to TL12-186 in all phases. These data indicate that target subpopulation degradation can occur, dictated by the formation of the ternary complex. These studies additionally underscore the importance of profiling degradation compounds in cellular systems where complete pathways are intact and target proteins can be characterized in their relevant complexes.

Thermal degradation kinetics study of molten polylactide based on Raman spectroscopy

AbstractThe thermal degradation of polylactide (PLA) during melt processing may lead to poor product properties. In this study, a unique Raman system was applied to explore the thermal degradation kinetics of molten PLA under five different temperatures and three atmospheres. It was found that the intensity of specific Raman bands correlated with the concentration of functional groups in the PLA during the degradation process. Kinetic models for thermal degradation were established based on the intensity of the characteristic band of C‐COO. Kinetic parameters determined by kinetic models quantitatively revealed the effect of temperature and atmosphere on thermal degradation. Furthermore, time sweep rheological tests using the same degradation conditions were performed for verification, and the results corroborated the spectral analyses. This investigation demonstrates the feasibility of Raman spectroscopy for thermal degradation kinetic analysis.

Heat-activated potassium persulfate treatment of Sudan Black B dye: Degradation kinetic and thermodynamic studies

Water-soluble dyes are common persistent organic pollutants present in textile wastewater, which are associated with environmental pollution and health hazards. The conventional effluent treatment methods are not efficient to remove these dyes from textile wastewater. Heat activated persulfate based wastewater treatment is a promising advanced oxidation process (AOP) for the treatment of textile wastewater. Therefore, the main objective of the present work was to study the degradation of Sudan Black B (SBB) dye in aqueous solution by varying activation temperature (40–60 °C), KPS dosage (250–750 ppm), and initial dye concentration (20–50 ppm). The dye degradation was found in a range of 35%−100% for varied experimental conditions. Removal percentages were improved by the increase of temperature, time, and persulfate concentration but decreased with the increase of initial dye concentration. The kinetic study indicated that the degradation of SBB dye using KPS followed first order model with rate constants varied in a range of 0.15 × 10-2 − 40.5 × 10-2 min-1. Standard reaction enthalpies (ΔH˚), standard Gibbs free energies (ΔG˚), activation energies (Ea), standard entropies (ΔS˚) were found in a range of 190 − 505 kJ.mole-1, -33.0 − 0.6 kJ, 73 − 222 kJ.mole-1, 0.6–1.6 kJ/K for different sets of experimental conditions, respectively. Degradation reactions of SBB dye were endothermic (ΔH˚ +ve); non-spontaneous (ΔG˚ +ve) at 40 °C, but spontaneous (ΔG˚ −ve) at other temperatures (50 °C and 60 °C). Therefore, it can be predicted that heat-activated persulfate is an efficient method to achieve faster degradation of dye in the treatment of industrial wastewaters containing SBB dye.

Development of α-Fe2O3/TiO2 3D hierarchical nanostructured photocatalysts through electrochemical anodization and sol–gel methods

Titanium dioxide (TiO2) nanotubes have attracted much attention due to their formation, properties, and functionality in recent years. Many methods have been used to obtain the nanotubes, such as template synthesis, hydrothermal, sol–gel, and electrochemical anodization. Compared to others, the electrochemical anodization method makes it possible to grow dense and well-aligned nanotube layers on pure and/or alloyed titanium surfaces. However, for enhanced photocatalytic activities, the parameters of the anodization process such as applied potential, time, and electrolyte composition should be tightly controlled to obtain regular, well-aligned, and continuous nanotube arrays. Alternatively, by the formation of heterojunctions such as α-Fe2O3/TiO2, the performances of the photocatalysts can be boosted due to the shifts of absorption range into the visible region and narrower band gaps of the hierarchical structures. In this study, TiO2 nanotubes were obtained by electrochemical anodization on Ti foil in ethylene glycol, ammonium fluoride and distilled water-based electrolyte under constant voltage and varying anodization durations. Herein, it was aimed to observe the effects of the anodization time on the length and diameter of the nanotubes, which have significant roles on the photocatalytic activity. Besides the investigation of the anodization parameters, the heterogeneous structure, α-Fe2O3/TiO2, was formed on anodized surfaces to scrutinize the improvement of the photocatalytic properties. The TiO2 nanotubes were characterized through XRD and SEM to determine the phase structure and morphology, respectively. The variation of optical bandgap values of α-Fe2O3/TiO2 samples depending on the processing parameters was determined by using a UV–Vis spectrophotometer. The photocatalytic performances of the α-Fe2O3/TiO2 photocatalysts were revealed using an aqueous solution of methylene blue. Photocatalytic degradation rates and kinetic study of α-Fe2O3/TiO2 photocatalysts were evaluated by a comparative approach. The highest degradation efficiency was achieved as 85% using the α-Fe2O3 coated photocatalyst with the anodization time of 30 min and anodization voltage of 30 V.

Study of thermal degradation behavior and kinetics of ABS/PC blend

Abstract This work investigated kinetics and thermal degradation of acrylonitrile butadiene styrene and polycarbonate (ABS/PC) blend using thermogravimetric analysis in the range of 25 to 520°C. For thermal degradation of blend, activation energy (E a ) and pre-exponential factor (A) were calculated under various heating rates as 5, 10, 15 and 20°C/min using iso-conversional model-free methods (Kissinger, Flynn-Wall- Ozawa and Friedman). Mass loss of the blend as a function of temperature was plotted as thermogravimetric curve (TG) while derivative values of mass loss were drawn as derivative thermogravimetric (DTG) curve. Using Kissinger method, E a was 51.4 kJ/mol, while values calculated from FWO and Friedman method were 86–161 and 30–251 kJ/mol respectively. Results showed increasing trend of E a with higher conversion values indicating different degradation mechanisms at the initial and final stages of the experiment. Thermodynamic parameters such as enthalpy change (ΔH), Gibbs free energy (ΔG) and entropy change (ΔS) were also calculated.

Design of Experiments (DoE) - Based Enhanced Quality by Design Approach to Hydrolytic Degradation Kinetic Study of Capecitabine by Eco-friendly Stability Indicating UV-Visible Spectrophotometry

Design of Experiments (DoE) - Based Enhanced Quality by Design Approach to Hydrolytic Degradation Kinetic Study of Capecitabine by Eco-friendly Stability Indicating UV-Visible Spectrophotometry

Thermal characterization and lifetime prediction of the PHBV/nanocellulose biocomposites using different kinetic approaches

In the present study, biocomposite films from cellulose nanocrystals (CNCs) were obtained by the solution casting method. CNCs were isolated from pineapple crown using chemical treatments followed by sulfuric acid hydrolysis and added into poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) matrix. The effect of freeze-dried CNC content (1, 3, and 5 wt%) on the structural, crystallization, thermal degradation lifetime prediction, and thermogravimetric simulation was investigated. An irreversible agglomeration observed after freeze-dried provided changes in the morphology and size of CNCs. Addition up to 3 wt% of CNCs increased the thermal stability, crystallization rate, and crystallinity index of PHBV, as showed by thermal and crystallinity analysis, respectively. The kinetic degradation study by thermogravimetric analysis (TGA) was done using the F-test method by statistically comparing degradation mechanisms in the solid-state. The most probable degradation mechanism was the autocatalytic reaction model for all samples (represented by Cn and Bna-types) with a suitable adjustment of the simulated curves. Lifetime prediction showed to be successfully applied based on the kinetic analysis, and PHBV reinforced with 3 wt% of CNCs presents the highest results for the isothermal temperature of 180 °C.

Study of Degradation Kinetics of Magnesium Orotate Dihydrate by Spectroscopic Method

In the present work, we developed and validated five spectrophotometric methods for determination of magnesium orotate dihydrate in distilled water, pH 1.2, 4.5, 6.8, and 7.4 buffer systems. These media were selected to extend the applicability of the developed methods from the development of dosage forms to regular quality control. In all media, linear correlation was observed over the concentration range from 1 to 25 μg/mL. The developed methods were found to be selective and specific to the determination of magnesium orotate dihydrate in the presence of various excipients, as well as accurate, precise, and robust (the percent relative standard deviation was found to be less than 2%, and the percent recoveries were between 98 to 102%). The developed methods were also found to be highly sensitive, since the detection and quantification limits were found to be less than 1 μg/mL. The degradation kinetics studies reveal the stability of magnesium orotate dihydrate against hydrolysis (acidic or basic), oxidation, photolysis, and thermal treatment.

The Degradation Kinetics Study of Aromatic Organics with Different Functional Compounds on Anatase 001 Surface

Anatase TiO2 photocatalysts with exposed (001) facets have attracted great attention for environmental protection technology due to their high reactivity for degradation of organic species. In this work, potassium hydrogen phthalate (denoted as KHP), as the most commonly used reference standard solution for calibrating photoelectrochemical chemical oxygen demand (denoted as PeCOD) instrument, was selected as the study sample. The intrinsic degradation kinetics of KHP on (001) surface was investigated by a photoelectrochemical (denoted as PEC) method with a purposely (001) faceted double-layered structure TiO2 photoanode. The high kinetics constants of fast process of KHP and other acids indicate that the (001) surface possesses a higher reactivity of aromatic carboxylic acid as theoretically predicted. Meanwhile, the investigation of the KHP adsorption properties on A001 photoanode provides the possibility of using this photoanode as a sensor in a new type of PeCOD instrument for organic acid determination.

Thermal degradation kinetic study of Pangasius fish oil

Pangasius fish oil is rich in unsaturated fatty acids that are beneficial for health. However, unsaturated fatty acids are easy degraded due to temperatures and oxidation. This study aimed to determine the changes in the quality of pangasius fish oil during heating and the result of oxidation value based on activation energy. Pangasius fish oil was heated at three different temperatures which were 70°C, 80°C, and 90°C for 15, 30, 45, 60, and 75 min. The observation includes peroxide value, TBA value, FFA, and fatty acid profiles. The results showed that higher temperatures and prolonged heating increased the peroxide value, TBA value, and FFA. The rate of quality degradation in pangasius fish oil proved by each activation energy of PV 111.433 kJ/mol, TBA 7.368 kJ/mol, and FFA 83.971 kJ/mol and unsaturated fatty acid, especially linolenic acid decreased. It showed that the oxidation during heating reduced the quality of pangasius fish oil.