A quick, direct method for the determination of activation energy from thermogravimetric data

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.

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New temperature fluctuation method for direct determination of thermal activation energy of deep levels in semiconductors

Electronics Letters ◽

10.1049/el:19830187 ◽

1983 ◽

Vol 19 (7) ◽

pp. 271 ◽

Cited By ~ 1

Author(s):

V. Kumar ◽

H. Indusekhar

Keyword(s):

Activation Energy ◽

Temperature Fluctuation ◽

Thermal Activation ◽

Direct Determination ◽

Thermal Activation Energy ◽

Deep Levels ◽

Fluctuation Method

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Cathodoluminescence of SiO2/Si System

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.156-158.487 ◽

2009 ◽

Vol 156-158 ◽

pp. 487-492 ◽

Cited By ~ 1

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.

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Determination of the membrane hydraulic permeability of MSCs

Current Directions in Biomedical Engineering ◽

10.1515/cdbme-2016-0072 ◽

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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The determination of the heat of dissociation of fluorine and of the latent heat of vaporisation of lithium

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1932.0067 ◽

1932 ◽

Vol 136 (829) ◽

pp. 76-82 ◽

Cited By ~ 6

Keyword(s):

High Temperature ◽

Absorption Spectra ◽

Latent Heat ◽

Chemical Reactivity ◽

Direct Method ◽

Thermal Methods ◽

Heat Of Dissociation

The heats of dissociation of chlorine, bromine, and iodine have been determined by thermal methods and estimated to be 58·9, 45·2 and 35·2 kilo-cals. respectively. But no data are yet known concerning the heat of dissociation of fluorine. It is very difficult to subject fluorine to the same treatment as Cl 2 , Br 2 and I 2 ( i. e ., heating to a high temperature in a sealed quartz bulb) owing to its extreme chemical reactivity, and hence no direct method of determining the heat of dissociation of fluorine has yet been devised. In the present paper I have determined it indirectly by interpretation of the absorption spectra of alkali fluorides (for the present only NaF and KF). A short theory of the experiment is given below.

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