Thermal Degradation Kinetics of N,N'-Di(diethoxythiophosphoryl)-1,4-phenylenediamine

The non-isothermal degradation kinetics of N,N＇-di（diethoxythiophosphoryl）-1,4-phenylenediamine in N2 was studied by TG-DTG techniques.The kinetic parameters,including the activation energy and pre-exponential factor of the degradation process for the title compound were calculated by means of the Kissinger and Flynn-Wall-Ozawa（FWO）method and the thermal degradation mechanism of the title compound was also studied with the Satava-Sestak methods.The results indicate that the activation energy and pre-exponential factor are 152.61 kJ/mol and 9.06×101 4s -1with the Kissinger method and 154.08 kJ/mol with the Flynn-Wall-Ozawa method,respectively.It has been shown that the degradation of the title compound follows a kinetic model of one-dimensional diffusion or parabolic law,the kinetic function is G（α）=α2and the reaction order is n=2.

Thermal Degradation Kinetics of Three Kinds of Representative Anthocyanins Obtained from Blood Orange

Cyanidin-3-glucoside, cyanidin-3-（6′′-malonyl）-glucoside, and cyanidin-3-glucoside-derived pyranoanthocyanins which were three major anthocyanins of blood orange, were obtained using a Toyopearl TSK HW-40S column chromatography. Then, thermal degradation kinetics of the three major anthocyanins was studied at selected temperatures （70, 80, and 90°C）. Degradation parameters such as k and t1/2 values were determined. The activation energy （Ea） values for cyanidin- 3-glucoside, cyanidin-3-（6′′-malonyl）-glucoside and cyanidin-3-glucoside-derived pyranoanthocyanin were 75.4, 79.5, and 81.7 kJ mol-1, respectively. Ea values suggested that cyanidin-3-glucoside-derived pyranoanthocyanin had the highest stability, followed by cyanidin-3-（6′′-malonyl）-glucoside and cyanidin-3-glucoside. However, t1/2 values indicated cyanidin- 3-glucoside-derived pyranoanthocyanin degraded faster than cyanidin-3-（6′′-malonyl）-glucoside and cyanidin-3-glucoside at selected temperature.

Thermal Degradation Kinetics of Anthocyanins and Visual Color of Blood Orange Juice

Thermal degradation kinetics of anthocyanins and visual color （Hunter α value） of blood orange juice were studied at selected temperatures （70-90℃）. Results indicated that both the thermal degradation of anthocyanin and visual color all followed first-order reaction kinetics, and they could be expressed by Arrhenius equation. The activation energy values for the anthocyanins degradation and visual color degradation were 55.81 and 47.51 kJ tool-1, respectively. The linear relationship between visual color and anthocyanin content was obtained. Furthermore, during thermal processing of blood orange juice, the formulas about the linear relationships showed no significant difference at selected temperatures. So, the relationships between visual color and anthocyanins content during thermal processing at selected temperatures could be described by the same equation： α＊/αo＇=0.559（C/Co）＋0.43. It might be inferred that visual color measured instantaneously by tristimulus colorimeters for on-line quality control, could be used to predict the anthocyanins degradation during thermal processing of blood orange juice.

Study on degradation kinetics of epalrestat in aqueous solutions and characterization of its major degradation products under stress degradation conditions by UHPLC-PDA-MS/MS

Drug stability is closely related to drug safety and needs to be considered in the process of drug production,package and storage.To investigate the stability of epalrestat,a carboxylic acid derivative,a reversed-phase high-performance liquid chromatography(RP-HPLC)method was developed in this study and applied to analyzing the degradation kinetics of epalrestat in aqueous solutions in various conditions,such as different pH,temperatures,ionic strengths,oxidation and irradiation.The calibration curve was A=1.6×10^5C–1.3×10^3(r=0.999)with the liner range of 0.5–24μg/mL,the intra-day and inter-day precision was less than 2.0%,as was the repeatibility.The average accuracy for different concentrations was more than 98.5%,indicating that perfect recoveries were achieved.Degradation kinetic parameters such as degradation rate constants(k),activation energy(Ea)and shelf life(t0.9)under different conditions were calculated and discussed.The results indicated that the degradation behavior of epalrestat was pH-dependent and the stability of epalrestat decreased with the rised irradiation and ionic strength;however,it was more stable in neutral and alkaline conditions as well as lower temperatures.The results showed that the degradation kinetics of epalrestat followed first-order reaction kinetics.Furthermore,the degradation products of epalrestat under stress conditions were identified by UHPLC-PDA-MS/MS,with seven degradation products being detected and four of them being tentatively identified.

Distribution and degradation kinetics of cyhalodiamide in Chinese rice field environment

Cyhalodiamide is a novel agrochemical which is effective against Lepidoptera pests,including Cnaphalocrocis medinalis,Chilo suppressalis,Pieris rapae,Plutella xylostella,Helicoverpa armigera,etc.In the study,a fast and accurate analytical method was developed to detect cyhalodiamide in Chinese typical rice field environment by a modified Qu ECh ERS(Quick,Easy,Cheap,Effective,Rugged,Safe)method with UPLC-MS/MS(ultra-high performance chromatography-tandem mass spectrometry).The mean recoveries of cyhalodiamide varied from 73.5% to 107.5%,with the RSDs from 1.2% to 10.7%.The limits of determination(LODs)were 0.0005 mg·kg^(-1),and the limits of quantitation(LOQs)were from 0.002 to 0.01 mg·kg^(-1)in all five matrices.This method was used to determine cyhalodiamide residues for studies of the distribution and degradation kinetics in rice field environment.The field trials results showed that cyhalodiamide was easily degradable and the half-lives were4.2–13.6 d in rice straw,8.77 d in paddy soil and 5.37–8.45 d in paddy water,respectively.The final residues of cyhalodiamide in brown rice were below 0.35 mg·kg^(-1).The used dosage of 33.75 g·hm^(-2)with pre-harvest interval(PHI)of 21 d and the maximum residue limit(MRL)of cyhalodiamide in rice at 0.1 mg·kg^(-1)were recommended,which would be safe to human health and environment.The developed analytical method will be useful to monitor cyhalodiamide residues and safety evaluation in rice environment.

Research on the Degradation Kinetics Model in the Drying Process of Chinese Herb

Curative compositions such as catolpol in Rehmannia Glutinosa, flavone in Ophiopogon Japonicus and ginsenoside Re in Panax Ginseng in Chinese herbs were measured as the experimental indices by the method of high performance liquid chromatography under different drying conditions. The reaction order and parameters of the degradation kinetics model were determined and the model was verified by experiments. It was indicated that by comparing with the thin drying method, the prospective model could predict the degradation of curative compositions with drying time, temperature and moisture content of herbal materials with enough precision and could be used to simulate the degradation in the drying process of Chinese herb.

STUDY OF ACONITINE DEGRADATION KINETICS IN RABBIT CORPSES

in order to research on the degradation kinetics rule or aconitine (AC) in rabbit corpses,in this article,through the acute intoxic models set up by orally administrating Aconitum brachypodum Diels (AbD) of absolute lethal dose (ALD) to New Zealand rabbits,the changing rules of aconitine degradation in tissues of rabbit corpses stored at 4℃ refrigirater were studied. The result showed that AC degradation process in rabbit corpses was apparent two-order degradation kinetics. AC degradation kinetics equations in liver and kidney were the half lives of them were 5.66 and 6. 47 days respectively.

Degradation kinetics of larotaxel and identification of its degradation products in alkaline condition

Larotaxel, a new taxane compound prepared by partial synthesis from 10-deacetyl baccatin III, is active against tumors. In this research, a selective LC–MS method was developed and validated for the study of degradation kinetics of larotaxel, which was carried out in aqueous solutions with different pH（1.5, 3.0, 5.0, 6.5, 7.4, 9.0, 10 and 11.0） and temperature（0, 25, 37 and 45 °C）. The linear range was 0.5–25 μg/mL, the intra-and inter-day precisions were less than 7.0%, and accuracy ranged from 97.4–104.5% for each analyte. The observed rate obtained by measuring the remaining intact larotaxel was shown to follow first-order kinetics. The activation energies for degradation were 126.7 and 87.01 k J/mol at pH 1.5 and 11, respectively. Although larotaxel was stable in pH 5, 6.5 and 7.4 buffers at 37 °C for 24 h during our study, increasing or decreasing the pH of the solutions would decrease its stabilities. Moreover, three main degradation products in alkaline condition were separated by HPLC and identified by Q–TOF–MS. The three degradation products were confirmed as 10-deacetyl larotaxel, 7, 8-cyclopropyl baccatin Ⅲ and 10-deacetyl-7, 8-cyclopropyl baccatin Ⅲ.

Efficient degradation of aqueous dichloromethane by an enhanced microbial electrolysis cell:Degradation kinetics,microbial community and metabolic mechanisms

Dichloromethane(DCM)has been listed as a toxic and harmful water pollutant,and its re moval needs attention.Microbial electrolysis cells(MECs)are viewed as a promising alterna tive for pollutant removal,which can be strengthened from two aspects:microbial inocula tion and acclimation.In this study,the MEC for DCM degradation was inoculated with the ac tive sludge enhanced by Methylobacterium rhodesianum H13(strain H13)and then acclimated in the form of a microbial fuel cell(MFC).Both the introduction of strain H13 and the initi ation in MFC form significantly promoted DCM degradation.The degradation kinetics were fitted by the Haldane model,with V_(max),K_(h),K_(i)and v_(max)values of 103.2 mg/L/hr,97.8 mg/L268.3 mg/L and 44.7 mg/L/hr/cm^(2),respectively.The cyclic voltammogram implies that DCM redox reactions became easier with the setup of MEC,and the electrochemical impedance spectrogram shows that the acclimated and enriched microbes reduced the charge transfe resistance from the electrode to the electrolyte.In the biofilm,the dominant genera shifted from Geobacter to Hyphomicrobium in acclimation stages.Moreover,Methylobacterium played an increasingly important role.DCM metabolism mainly occurred through the hydrolytic glutathione S-transferase pathway,given that the gene dcmA was identified rather than the dhlA and P450/MO.The exogenous electrons facilitated the reduction of GSSG,directly o indirectly accelerating the GSH-catalyzed dehalogenation.This study provides support fo the construction of an efficient and stable MEC for DCM removal in water environment.

Interface and mechanical degradation mechanisms of the silicon anode in sulfide-based solid-state batteries at high temperatures

Silicon(Si)is a competitive anode material owing to its high theoretical capacity and low electrochemical potential.Recently,the prospect of Si anodes in solid-state batteries(SSBs)has been proposed due to less solid electrolyte interphase(SEI)formation and particle pulverization.However,major challenges arise for Si anodes in SSBs at elevated temperatures.In this work,the failure mechanisms of Si-Li_(6)PS_(5)Cl(LPSC)composite anodes above 80℃are thoroughly investigated from the perspectives of interface stability and(electro)chemo-mechanical effect.The chemistry and growth kinetics of Lix Si|LPSC interphase are demonstrated by combining electrochemical,chemical and computational characterizations.Si and/or Si–P compound formed at Lix Si|LPSC interface prove to be detrimental to interface stability at high temperatures.On the other hand,excessive volume expansion and local stress caused by Si lithiation at high temperatures damage the mechanical structure of Si-LPSC composite anodes.This work elucidates the behavior and failure mechanisms of Si-based anodes in SSBs at high temperatures and provides insights into upgrading Si-based anodes for application in SSBs.

Degradation kinetics of functional components of honeysuckle flowers during controlled-atmosphere heat pump drying

To investigate the change law of functional components and exterior color of honeysuckle flowers(HF)during controlled-atmosphere heat pump drying,nitrogen was used as drying medium in this study to reduce the oxygen concentration.The influences of drying temperature,HF’s loading amount and oxygen concentration on chlorogenic acid content,cynaroside content and L value(on behalf of browning degree)were explored,and the degradation kinetics models of chlorogenic acid and cynaroside were constructed.The results showed that chlorogenic acid content,cynaroside content and L value decreased with the rise of temperature,HF’s loading amount and oxygen concentration.The degradation kinetics models of chlorogenic acid and cynaroside during the drying process were established through introducing an exponent r related to time t in the first order reaction kinetics equation.The models had good fitting precision and can be used to predict the degradation law of chlorogenic acid and cynaroside.

Thermal Degradation Kinetics of Structurally Diverse Poly(bispropargyl ethers-bismaleimide) Blends

Structurally diverse bispropargyl ethers using resorcinol,quinol,4,4￠-dihydroxy biphenyl,bisphenol-A,4,4￠-dihydroxy diphenyl ketone,4,4￠-dihydroxy diphenylsulphone,trimethyl indane bisphenol and tetramethyl spirobiindane bisphenol were prepared by using phase transfer catalyst.Synthesized materials were separately blended with 4,4￠-bismaleimido diphenyl methane（BMIM）in mole ratios（0.5：0.5）.The materials were thermally cured and the structural characterisation and the thermal properties of these cross-linked materials are investigated using Fourier-transform infrared（FTIR）spectrophotometer and thermogravimetric analyzer（TGA）.Among the different materials investigated poly MRPE,poly MBPEBPA and poly MSPE show higher onset degradation temperature of 300°C indicating higher thermal stability.The degradation kinetics is investigated using Flynn-Wall-Ozawa（FWO）,Vyazovkin（VYZ）and Friedman（FRD）methods.Amongst the various cured materials investigated,the activation energy（Ea-D）values obtained for poly MRPE and poly MKPE were observed to increase continuously froma=0.2 to 0.8 and the values range from 199 kJ/mol to 245 k J/mol and 153 k J/mol to 295 k J/mol respectively.The crosslinked materials resulting from these bispropargyl monomers definitely need more energy for bond cleavage due to the presence of more aromatic units.The volatile products obtained during the thermal degradation of the polymers were analyzed using thermogravimetric-Fourier transform infrared analyses（TG-FTIR）.The phenols,substituted phenols,carbon monoxide,carbon dioxide and small amount of aniline were found to be the major products during thermal degradation of these cured blends.

Thermal degradation kinetics and lifetime estimation for polycarbonate/polymethylphenylsilsesquioxane composite

The thermal degradation behaviors of poly-carbonate/polymethylphenylsilsesquioxane(FRPC)com-posites were investigated by thermogravimetric analysis(TGA)under isothermal conditions in nitrogen atmo-sphere.The isothermal kinetics equation was used to describe the thermal degradation process.The results showed that activation energy(E),in the case of isothermal degradation,was a quick increasing function of conversion(α)for polycarbonate(PC)but was a strong and decreasing function of conversion for FRPC.Under the isothermal condition,the addition of polymethylphenylsilsesquioxane(PMPSQ)retardanted the thermal degradation and enhanced the thermal stability of PC during the early and middle stages of thermal degradation.It also indicated a possible existence of a difference in nucleation,nuclei growth,and gas diffusion mechanism in the thermal degradation process between PC and FRPC.Meanwhile,the addition of PMPSQ influenced the lifetime of PC,but the composite still met the demand in manufacturing and application.

Kinetics study of metaxalone degradation under hydrolytic, oxidative and thermal stress conditions using stability-indicating HPLC method

An isocratic stability indicating RP-HPLC-UV method is presented for the determina- tion of metaxalone （MET） in the presence of its degradation products. The method uses Dr. Maisch C18 column （250 mm × 4.6 mm, 5μm） with mobile phase consisting of acetonitrile-potassium dihydrogen orthophosphate buffer with 4 mL of 0.4% triethyl amine （pH 3.0; 10 mM） （58：42, v/v） at a flow rate of 1.0 mL/min, pH of the buffer was adjusted with o-phosphoric acid. UV detection was performed at 225 nm. The method was validated for specificity, linearity, precision, accuracy, limit of detection, limit of quantification and robustness. The calibration plot was linear over the concentration range of 1-100 μg/mL having a correlation coefficient （r2） of 0.999. Limits of detection and quantification were 0.3 and 1μg/mL, respectively. Intra-day and inter-day precision （% RSD） was 0.65 and 0.79 respectively. The proposed method was used to investigate the degradation kinetics of MET under different stress conditions employed. Degradation of MET followed a pseudo-first-order kinetics, and rate constant （K）, time left for 50% potency （t1/2）, and time left for 90% potency 090） were calculated.

Degradation of Anionic Dye Eosin by Glow Discharge Electrolysis Plasma

This paper describes a novel method for the degradation of eosin by using glow discharge electrolysis （GDE）. The effects of various parameters on the removal efficiency were studied. It was found that the eosin degradation could be raised considerably by increasing the applied voltage and the initial concentration, or by decreasing pH of the aqueous solution. Fe^2＋ ion had an evident accelerating effect on the eosin degradation. The degradation process of eosin obeyed a pseudo-first-order reaction. The relationship between the degradation rate constant k and the reaction temperature T could be expressed by Arrhenius equation with which the apparent activation energy Ea of 14.110 kJ· mol^-1 and the pre-exponential factor k0 of 2.065× 10^-1 min^-1 were obtained, too. The determination of hydroxyl radical was carried out by using N, N-dimethyl -p-nitrosoaniline （RNO） as a scavenger. The results showed that the hydroxyl radical plays an important role in the degradation process.

POSTMORTEM REDISTRIBUTION KINETICS OF ACONITINE IN RABBITS

The postmortem redistribution of aconitine(AC) and its influencing factors by orally ingested Aconitum brachypodum Diels (AbD) in rabbits were studied. The results showed that postmortem AC redistribution did exist, and the diffusion along a concentration gradient was the major influencing factor on it. Change of temperature and incomplete distribution in life also influenced it.Besides those mentioned above, there were other influencing factors. These may be related to postmortem blood movement and toxin released from cells occurring as part of the processes of autolysis and putrefaction.

Degradation characteristics of two Bacillus strains on the Microcystis aeruginosa

The degradation kinetics of strains P05 and P07 and the degradation effects of mixed strain on Microcystis aeruginosa were studied. The results showed that: (1) The degradation processes of strains P05 and P07 on Microcystis aeruginosa accorded with the first-order reaction model when the range of Chl-a concentration was from 0 to 1500 μg/L. (2) The initial bacterium densities had a strong influence on the degradation velocity. The greater the initial bacterium density was, the faster the degradation was. The degradation velocity constants of P05 were 0.1913, 0.2175 and 0.3092 respectively, when bacterium densities were 4.8×10 5, 4.8×10 6, 2.4×10 7 cells/ml. For strain P07, they were 0.1509, 0.1647 and 0.2708. The degradation velocity constant of strain P05 was higher than that of P07 when the bacterium density was under 4.8×10 5 cells/ml, but the constant increasing of P07 was quicker than that of P05. (3) The degradation effects of P05 and P07 strains did not antagonize. When the concentration of Chl-a was high, the degradation effects of mixed strain excelled that of any single strains. But with the decrease of the Chl-a concentration, this advantage was not clear. When the concentration was less than 180 μg/L, the degradation effects of mixed were consistent with that of strain P07.

Degradation kinetic study of lysine in lysine hydrochloride solutions for injection by determining its main degradation product

A limited number of researches have been reported to apply the Arrhenius equation to study the relationship between drugs and its degradation products so far.In the present work,the thermal degradation kinetics of lysine hydrochloride solutions for injection,the special solvent for ademetionine 1,4-butanedisulfonate(SAM)for injection,was investigated at selected temperatures and pH values.The main degradation product of lysine was separated,purified,and confirmed as lysine lactam.A reversed-phase high performance liquid chromatographic(RP-HPLC)method without derivation was developed for the simultaneous determination of lysine and lysine lactam.The results confirmed that both the lysine degradation and lysine lactam generation followed zero-order reaction kinetics.The degradation and generation rate constants increased with increasing temperatures and decreasing pH values.The temperature-dependent degradation and generation reaction could be sufficiently modeled on the Arrhenius equation with the activation energy of 80.14 and 83.22 kJ/mol,respectively.Meanwhile,a linear relationship existed between the amount of lysine degradation and lysine lactam generation since the approximate activation energy.Considering there could be other side effects,we established an upper limit of lysine lactam(500 mg/ml),as the acceptable criteria for stability to estimate the shelf life together with lysine,which made the prediction more accurate and credible.Extrapolation data demonstrated that the lysine hydrochloride solutions for injection could be stable for two years stored at room temperature.

Biodegradation of DTP and PET Fiber by Microbe

The degradation of diethylene glycol terephthalate (DTP) and polyethylene terephthalate (PET) fiber by microbe was studied.The degree of DTP degradation was determined by High Performance Liquid Chromatography (HPLC) to be more than 90%.The products after degradation of DTP and PET fiber were various.The degradation of DTP can be described by the first-order reaction model.The degradation of PET fiber was found to be little,but surface erosion of PET fiber could be clearly seen from the SEM photographs indicating there occurred some traces of biodegradation on the PET fiber surface.

Insight into the degradation mechanism of cefixime under crystallization condition

The chemical stability of cefixime was determined by high-performance liquid chromatography （HPLC） under different conditions, including factors such as pH, solvents, initial concentration, temperature and additives. The degradation process follows the first-order kinetics. A pH-rate profile exhibits the U-shape and shows the maximum stability of cefixime at pH = 6. The stability in different pure solvents is ranked as acetone 〉 ethanol 〉 methanol 〉 water, while the degradation rate of cefixime exists a maximum at the ratio of 0.6 in water ＋ methanol mixtures. In addition, the degradation rate increases with the temperature increasing and the activation energy of degradation was found to be 27.078 kJ. mol- 1 in acetone ＋ water mixed solvents. The addition of different additives was proven to either inhibit or accelerate the degradation. The degradation products were analyzed using HPLC, LC-MS and infrared spectroscopy, and the possible degradation pathways in acid as well as alkaline environment were proposed to help us understand the degradation behavior of cefixime.