A new iterative linear integral isoconversional method for the determination of the activation energy varying with the conversion degree

2009 ◽  
Vol 30 (13) ◽  
pp. 1986-1991 ◽  
Author(s):  
Junmeng Cai ◽  
Siyu Chen
Keyword(s):  
Activation Energy ◽  
Isoconversional Method ◽  
Conversion Degree ◽  
Linear Integral

Development of HPLC Method for the Purity Test by Design of Experiments and Determination of Activation Energy of Hydrolytic Degradation Reactions of Sofosbuvir

2020 ◽  
Vol 16 (7) ◽  
pp. 976-987
Author(s):  
Jakub Petřík ◽  
Jakub Heřt ◽  
Pavel Řezanka ◽  
Filip Vymyslický ◽  
Michal Douša
Keyword(s):  
Activation Energy ◽  
Design Of Experiments ◽  
Mobile Phase ◽  
Hydrolytic Degradation ◽  
Isoconversional Method ◽  
Hplc Method ◽  
Organic Modifier ◽  
Calculation Methods ◽  
Degradation Reactions

Background: The present study was focused on the development of HPLC method for purity testing of sofosbuvir by the Design of Experiments and determination of the activation energy of hydrolytic degradation reactions of sofosbuvir using HPLC based on the kinetics of sofosbuvir degradation. Methods: Following four factors for the Design of Experiments were selected, stationary phase, an organic modifier of the mobile phase, column temperature and pH of the mobile phase. These factors were examined in two or three level experimental design using Modde 11.0 (Umetrics) software. The chromatographic parameters like resolution, USP tailing and discrimination factor were calculated and analysed by partial least squares. The chromatography was performed based on Design of Experiments results with the mobile phase containing ammonium phosphate buffer pH 2.5 and methanol as an organic modifier. Separation was achieved using gradient elution on XBridge BEH C8 at 50 °C and a flow rate of 0.8 mL/min. UV detection was performed at 220 nm. The activation energy of hydrolytic degradation reactions of sofosbuvir was evaluated using two different calculation methods. The first method is based on the slope of dependence of natural logarithm of the rate constant on inverted thermodynamic temperature and the second approach is the isoconversional method. Results and Conclusion: Calculated activation energies were 77.9 ± 1.1 kJ/mol for the first method and 79.5 ± 3.2 kJ/mol for the isoconversional method. The results can be considered to be identical, therefore both calculation methods are suitable for the determination of the activation energy of degradation reactions.

Evaluation of activation energy of epoxy resin grafted with polyurethane using modified non-linear integral isoconversional method

2014 ◽  
Vol 18 (sup4) ◽  
pp. S4-466-S4-472
Author(s):  
Z. J. Song ◽  
J. L. Xie ◽  
Q. Lin ◽  
Z. H. Cao ◽  
X. L. Weng ◽  
...  
Keyword(s):  
Activation Energy ◽  
Epoxy Resin ◽  
Isoconversional Method ◽  
Non Linear ◽  
Linear Integral

Iso-Conversional and Isokinetic Methods of Analysis of Non-Isothermal Crystallization in Ti50Cu20Ni30 Metallic Glass

2011 ◽  
Vol 171 ◽  
pp. 107-119
Author(s):  
Heena Dhurandhar ◽  
T. Lilly Shanker Rao ◽  
Kirit N. Lad ◽  
Arun Pratap
Keyword(s):  
Metallic Glass ◽  
Isoconversional Methods ◽  
Isoconversional Method ◽  
Scanning Calorimetry ◽  
Model Free ◽  
True Value ◽  
Linear Differential ◽  
Linear Integral ◽  
Kinetics Of

The crystallization kinetics of metallic glass Ti50Cu20Ni30 has been studied using Differential Scanning Calorimetry (DSC). The DSC thermograms have been analysed using the model-free isoconversional methods and model dependent isokinetic methods. The activation energy(E) for the crystallization process has been determined utilizing; (i) various linear integral isoconversional methods, namely, Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose, Li Tang method (ii) linear differential isoconversional method and (iii) different isokinetic methods. In the present work, we intend to the determination of true value of E. The above methods are found to give consistent results for E.

Cathodoluminescence of SiO2/Si System

2009 ◽  
Vol 156-158 ◽  
pp. 487-492 ◽  
Author(s):  
M.V. Zamoryanskaya
Keyword(s):  
Activation Energy ◽  
Electron Beam ◽  
Rise Time ◽  
Silicon Oxide ◽  
Beam Current ◽  
Electron Beam Current ◽  
Electron Traps ◽  
Definition Of ◽  
Luminescent Centers

In this paper the new method for determination of luminescent centers concentration are discussed. While the possibility of electron traps determination and definition of its activation energy are suggested. The cathodoluminescent (CL) method was used. The determination of luminescent centers concentration in silicon oxide is based on the measurements of dependences of CL intensity on electron beam current. The presence and energy of activation of electron traps were studied by measurement of rise time and decay of luminescent band during the stationary irradiation of silica by electron beam.

scholarly journals Determination of the membrane hydraulic permeability of MSCs

2016 ◽  
Vol 2 (1) ◽  
pp. 323-327
Author(s):  
Jennifer Contreras Lopez ◽  
Lothar Lauterböck ◽  
Birgit Glasmacher
Keyword(s):  
Activation Energy ◽  
Bone Marrow ◽  
Cooling Rate ◽  
Mesenchymal Stromal Cells ◽  
Stromal Cells ◽  
Hydraulic Permeability ◽  
Osmotic Behaviour ◽  
Additional Influence ◽  
Dimethyl Sulfoxid

AbstractA successful cryopreservation is based on knowledge of the optimal cooling rate. So far, this is often determined by way of complex parameter studies. Alternatively, the identification of cell specific characteristics, such as osmotic behaviour, membrane hydraulic permeability and activation energy could be used to calculate the optimal cooling rate. These parameters should be determined for supra-zero and sub-zero temperatures. In this study cryomicroscopy was used. Mesenchymal stromal cells (MSCs) from bone marrow were analysed. The determined membrane hydraulic permeability for sub-zero temperatures is significantly lower than that for supra-zero temperatures. On the contrary the activation energy is significantly higher in the presence of ice. The addition of a cryoprotective agent (CPA) such as dimethyl sulfoxid (DMSO) shows an additional influence on the characteristics of the membrane of the cell. The optimal cooling rate was determined with these parameters. For cryopreservation without DMSO the optimal cooling rate was found to be 12.82 K/min. If the MSCs were frozen with 5% (v/v) DMSO the optimal cooling rate is 16.25 K/min.

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