Efficient Method for the Determination of the Activation Energy of the Iodide-Catalyzed Decomposition of Hydrogen Peroxide

2014 ◽  
Vol 91 (8) ◽  
pp. 1216-1219 ◽  
Author(s):  
William Sweeney ◽  
James Lee ◽  
Nauman Abid ◽  
Stephen DeMeo
2011 ◽  
Vol 277 ◽  
pp. 120-128
Author(s):  
Nofrijon I. Sofyan

Determination of copper dissolution activation energy in concentrated hydrogen peroxide used as a decontaminant agent on aircraft has been carried out. This work was performed in conjunction with the determination of the effect of hydrogen peroxide used as a decontaminant agent on selected aircraft metallic materials. The main idea of this work was to simulate the worst possible condition, i.e. spillage of the liquid concentrate due to operator abuse or conditions where large-scale condensation of the peroxide takes place due to the failure of decontamination process control. Due to inherent properties of the chemical used as a decontaminant agent, it possibly could affect the airliner metallic materials during or after the decontamination process, particularly copper. Since copper is one of the important alloying elements in the aluminum alloys, this work was performed to get the idea how fast the process takes place and so to help understanding the subsequent corrosion process, if any, on the aircraft’s flightworthiness at least qualitatively and ideally quantitatively. The results showed that the rate of copper dissolution increased for the first 15 minutes of the reaction time with an activation energy of 19 kJ/mol, and then the fraction of copper dissolved became constant. This constant dissolution was expected to be due to the formation of copper hydroxide, which was observed to precipitate after the solution settled for some time. However, because the final consumption of hydrogen peroxide was not controlled, the exact reason for this constant dissolution cannot be determined at this time. The value of activation energy is within the range of activation energy found in the literature for other dissolution process. The low activation energy for dissolution of pure copper correlates with the observation of dissolution of copper from intermetallic particles in the aluminum alloys.


2020 ◽  
Vol 16 (7) ◽  
pp. 976-987
Author(s):  
Jakub Petřík ◽  
Jakub Heřt ◽  
Pavel Řezanka ◽  
Filip Vymyslický ◽  
Michal Douša

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.


1983 ◽  
Vol 29 (8) ◽  
pp. 1513-1517 ◽  
Author(s):  
M W McGowan ◽  
J D Artiss ◽  
B Zak

Abstract A procedure for the enzymatic determination of lecithin and sphingomyelin in aqueous solution is described. The phospholipids are first dissolved in chloroform:methanol (2:1 by vol), the solvent is evaporated, and the residue is redissolved in an aqueous zwitterionic detergent solution. The enzymatic reaction sequences of both assays involve hydrolysis of the phospholipids to produce choline, which is then oxidized to betaine, thus generating hydrogen peroxide. The hydrogen peroxide is subsequently utilized in the enzymatic coupling of 4-aminoantipyrine and sodium 2-hydroxy-3,5-dichlorobenzenesulfonate, an intensely red color being formed. The presence of a non-reacting phospholipid enhances the hydrolysis of the reacting phospholipid. Thus we added lecithin to the sphingomyelin standards and sphingomyelin to the lecithin standards. This precise procedure may be applicable to determination of lecithin and sphingomyelin in amniotic fluid.


Author(s):  
Vitor Vaz de Melo Antipoff ◽  
Rosimeire Resende dos Santos ◽  
Daniella Vasconcellos Augusti ◽  
Zenilda de Lourdes Cardeal ◽  
Helvécio Costa Menezes

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